Friday 26 June 2020

Edward Bles. Part 4. Cambridge: Olms and Paul Kammerer

At the end of April 1923, 12 Madingley Road had a house guest. Edward and Bertha Bles were entertaining Paul Kammerer who had been invited to give a talk to the Cambridge Natural History Society about his claims on the inheritance of acquired characteristics. Bles and Kammerer would have had much to talk about since both kept and bred amphibians, and three of Kammerer’s claims centred on such species, the Midwife Toad (Alytes obstetricans), the Fire Salamander (Salamandra salamandra) and, to a certain extent, the Olm (Proteus anguinus).

The lecture at Cambridge provided the opportunity for a verbal punch-up between the neo-Darwinists and the neo-Lamarckians. Discussion at the time was concerned with the possibility that the scientific world was being gulled by a plausible fraudster. Despite the efforts of some to resurrect Kammerer’s reputation, notably the mystic and over-taken-notice-of Arthur Koestler with his book, The Case of the Midwife Toad, informed opinion seems to have swayed towards the view that Kammerer’s studies were fraudulent since there are plausible explanations as to how he, possibly with the assistance of others, had contrived to present doctored evidence that favoured his Lamarckian hypothesis.

There is a letter from George Albert Boulenger mentioned in Koestler’s book stating that Bles had visited Kammerer in Vienna at some time around 1908, so their meeting, at which all parties would have spoken German given Kammerer’s limited conversational English, would have been an opportunity to catch up. It would have been interesting to know if Hans Gadow (1855-1928) was also present. He helped Kammerer by translating the discussion at the Cambridge lecture but was not impressed by his science. Gadow was another amphibian enthusiast, notably writing the classic volume in the Cambridge Natural History series, but also keeping and breeding them at his house Cleramendi (since renamed) on Hinton Way at Great Shelford. I get the impression that Bles and Gadow were close; they operated as a team as two of the local organsers of the 1898 zoological congress held in Cambridge.

Both Kammerer and Bles had kept Olms, the cave-dwelling blind salamander of south-eastern Europe. Kammerer claimed to have bred them in captivity, a claim now strongly disputed since his ‘findings’ bear no relation to what has been observed either before or since, i.e. that they are viviparous and breed every year or so. Both had found that when kept in the light, the normally white animals turn black. Bles got there first on that one since Hans Gadow in his book published in 1901 wrote:

Mr. Bles has succeeded in producing several totally black specimens, having kept them for several months in a white basin under ordinary conditions of light. No experiments have yet been made to find out if the black pigment deposited is lost again in darkness.

Kammerer also claimed that eyes became larger when they were kept under alternating red light and daylight. When the skin over the eyes was removed, a specimen with normal eyes was produced. An alternative explanation, that he might have obtained such a specimen from a natural population in this highly variable species, has been advanced. However, Kammerer does not appear to have claimed that Olms with eyes or which had turned black produce young with these characteristics, as some neo-Lamarckists seem to have imagined.

Embed from Getty Images

In a previous post (here) I have described how it was intended to repeat and extend Kammerer’s experiments with Olms at London Zoo in the 1930s under the direction of Ernest W. MacBride, arch-lamarckist, Kammerer’s vicar on earth and a powerful, dogmatic but totally misguided figure in British science during the early decades of the 20th century. He also, incidentally, assumed the role of ‘Master of Ceremonies’ at the Cambridge lecture where it was said, ‘old MacBride’s ridiculous ex-cathedra statements did not help’.

Edward Bles was reported as having found Kammerer ‘absolutely honest’. However, he was clearly not convinced by what he had been told or had seen. After all he did insist that the chair he funded at Cambridge should be named after Darwin.

Bles did not live long enough to see the sad end of Kammerer; he died suddenly on 3 May 1926. Three months later, on 7 August, a letter to Nature by Gladwyn Kingsley Noble (1894 –1940) appeared. It delivered a bombshell: the alleged black nuptial pad of the only specimen of Kammerer’s Midwife Toad that was said to have survived was Indian Ink. Kammerer shot himself and was found dead on an Austrian mountain path on 23 September.

Alphen JJM van, Arntzen JW. 2016. Paul Kammerer and the inheritance of acquired characteristics. Contributions to Zoology 85, 457-470.

Gadow H. 1901. Amphibia and Reptiles. The Cambridge Natural History Volume VIII. London: Macmillan

Koestler A. 1971. The Case of the Midwife Toad. London: Hutchinson.

Thursday 25 June 2020

Edward Bles. Part 3. Mr Budgett’s Frogs and an abortive expedition to Paraguay

John Samuel Budgett died, aged 31, on 19 January 1904 of blackwater fever and malaria. He became famous because of his four expeditions to Africa in search of eggs and developing young of the strange fish, Polypterus. There had been all sorts of theories about Polypterus: that it was the ‘missing link’ between fish and amphibia; that it might even been an amphibian. Thomas Henry Huxley had considered it closely related to the the lungfish and the coelacanths, other fish with lobed fins. Eventually Budgett succeeded but did not live to present or publish the results. On the day of his death he was due to give paper to the Zoological Society of London. Polypterus is an ‘early’ finned fish, nowhere near any possible line of descent from fish to amphibian.

Budgett was following the Cambridge tradition established in the 1870s and 80s of using embryology as a tool to unravel evolutionary relationships. An exponent of the Cambridge embryological approach was John Graham Kerr. As a new graduate seeking to work on the lungfish, Lepidosiren, Kerr took Budgett on a collecting expedition in 1896/97 to the Paraguayan Chaco in order to collect material. During their trip Budgett also collected amphibians and reptiles. He found two new species, one of which. Lepidobatrachus laevis, is known as Budgett’s frog.

Budgett collected eggs and tadpoles in Paraguay as well as in Africa during his searches for Polypterus. Before his death he had worked on the development of one species collected in the Chaco. However, he left a great deal of material in Cambridge. At the time of Budgett’s death Kerr had moved from Cambridge to Glasgow, taking Edward Bles with him. Bles started to work on the eggs and tadpoles collected by Budgett both in South America and in Africa. Bles’s words take up the story:

When this material was handed over to me I was much impressed by its interesting character and still further impressed by the novelty of the Engystomid [narrow-mouthed] embryos of Hemisus and, as the series of stages of the last two forms were not extensive, I determined to make an effort to obtain more material and obtained six months leave for a voyage to S. America. I spent almost the whole of the time available—May to August 1905—at San Bernardino on Lake Ipacaraÿ in Paraguay. Unfortunately the winter was most exceptionally cold and there were great floods over immense tracts in Brazil, Paraguay, and the Argentine Republic. Lake Ipacaraÿ had also flooded its shores and my main objects, to collect vertebrate embryological material, were completely defeated. The frogs did not breed during that winter in Paraguay, the only tadpoles found were late hibernating stages. 

The area he chose was where Kerr and Budgett had collected nearly ten years earlier.  The eggs and tadpoles Bles was hoping to collect is now known as Physalaemus biligonigerus, the Four-eyed Weeping Frog. To get to Paraguay he sailed with his wife from Liverpool on 30 March 1905 on the S.S. Oravia heading for Buenos Aires. After what must been an extremely disappointing few months they arrived back in U.K. on 5 August, disembarking at Southampton from the S.S. Danube. Bles had suffered the well-known syndrome of ‘you should have been here last week/month/year; we were falling over them’.

Physalaemus biligonigerus (Raúl Maneyro)

The African species Budgett collected was Hemisus marmoratus, the Marbled Snout-burrower or Pig-nosed Frog or even Shovel-nosed Frog. Bles wrote up the description of the development of both species for a chapter in a memorial volume in honour of Budgett and his achievements compiled and edited by Kerr. Kerr himself completed the Polypterus story. Cambridge University Press published the book in 1907; it was reprinted in 2014.

Hemisus marmoratus (Ryanvanhuysteen)

John Samuel Budgett

Bles EJ. 1907. Notes on anuran development: Paludicola, Hemisus and Phyllomedusa. In The Work of John Samuel Budgett, Balfour Student of the University of Cambridge. Edited by J. Graham Kerr, pp 443-458 plus 6 plates. Cambridge University Press.

Tuesday 23 June 2020

Edward Bles (1864-1926). Part 2. Gentleman zoologist. Frogs, plankton, embryos and protozoa

Edward Bles was a zoologist with a substantial private income. He did not need to work but did so anyway, eventually in his own private laboratory. As described in Part 1 he was the first to describe the development of Xenopus in detail. Indeed much of his his work was in embryology at a time when this field was a leading and often controversial aspect of zoological research. Confusing for genealogists, he was known as Edward Jeremiah Bles but his birth was registered as Jeremiah Edward. Therefore, some documents do not fall immediately to hand when searching the historical records.

Bles was born in Salford near Manchester in 1864, the son of Abraham Jeremiah Samuel Bles (1838-1909) and Esther Polak. Abraham and his brother, David Samuel, were born in The Hague; their father established S.D. Bles & Co, merchants and shippers, in Machester largely for the Dutch trade. The Bles’s were leading lights in the Jewish community in Manchester as well as looking after the interests of the Dutch. Abraham was Dutch Consul.

In 1876 the Manchester Courier reported that young Bles had passed the Government Science Examination. Aged 14, Edward Bles was sent to a school in Hanover and at 18 started work in the family business. An interest in science which developed at school in Germany led to his joining the Manchester Microscopical Society (still in existence) of which he became Secretary. Such clubs brought amateurs and professionals together and it was there that Bles fell under the influence of Arthur Milnes Marshall FRS (1852-1893) who, in 1879 at the age of 27 had been appointed to the new chair of zoology in Owens College (later incorporated into what is now the University of Manchester). Bles therefore became a student at the college. In 1890 Bles published with Marshall papers on the development of amphibians, in this case the kidneys and fat bodies, and the blood vessels.

From Owens College, he moved to King’s College, London, graduating with a B.Sc in 1890. His obituarist (see below) noted that he spent time at the Naples marine laboratory but returned to Manchester, as junior demonstrator in zoology. In the summer of 1892 he was working at the Plymouth laboratory of the Marine Biological Association on plankton. He is shown in the resulting paper as honorary research fellow at Owens College. Bles must have been well known in the Plymouth laboratory because he was appointed Director in April 1893. But this was at a time of financial stringency. The Director had a heavy administrative load which prevented personal research. These factors resulted in a rapid turnover of Directors. Bles left in 1894. However, there may have been other reasons. In his second report as Director he noted that the issue of the Association’s journal was late: ‘Unforeseen circumstances affecting myself have caused a further postponement’. Were these ‘unforeseen circumstances’ and leaving Plymouth related to illness, which dogged him in later years, or to the fact that he married Bertha Bachmann of Augsberg in Dusseldorf, Germany on 12 November 1893?

October 1896 saw him admitted to King’s College, Cambridge at the age of 32. He graduated B.A. (as a research degree—the Ph.D, ‘the German degree’ was not awarded in Cambridge until 1921) in 1898 (M.A. 1907). In 1902 John Graham Kerr left Cambridge to the chair of natural history in Glasgow taking Bles (and his frogs) with him as senior assistant, which would be the equivalent of senior lecturer in English universities.

After 5 years in Glasgow, by which time he had been awarded the D.Sc. degree (by the University of London in 1906) and elected to the Royal Society of Edinburgh in 1904, Bles moved out of academia. First he moved to the Hill House, Iffley, Oxford and then to Cambridge where he and Bertha lived at ‘Elterholm’, 12 Madingley Road—a very large house. It would appear it was there that he further equipped his laboratory and ‘started to breed various species of rare amphibia, a difficult enterprise in which he had the assistance of his devoted wife’.

By that time he was also working on Arcella, a freshwater protozoan, in particular the role and control of the gas vacuoles which regulate its buoyancy. Bles had a marked determination not to rush into print. Although he had virtually completed the work by 1914, his long paper was not published until after his ‘very sudden’ death on 3 May 1926. Bertha, who died in 1960, had again helped Bles with is research and she helped with publication. Over the years it has been widely cited. He had again commissioned Kirkpatrick Maxwell to draw the plates.

One of the plates from Bles's paper
on Arcella which was published
three years aftere hisa death

Here is Bles’s words is a description of a part of this work:

These uniformly positive results strongly support the view, which has long been held, that the function of the gas-vacuoles is to reduce the specific gravity of the Arcella, and float it up to the surface which is rich in dissolved oxygen. But it is now possible to go a step farther. In considering the natural causes, or changes in the environment, which might possibly stimulate gas formation for hydrostatic purposes in Arcella, the first consideration was, what is the most obvious and most important physiological difference between the water at the bottom and the water under the surface-film? This is clearly a difference in oxygen pressure. The analyses of pond-water for the determination of dissolved gases carried out by Knauthe (1898, 1899) and Zuntz (1900) show that pond-water may, by the influence of physical and biological conditions, be entirely deprived of oxygen. Owing to the slow rate of diffusion of oxygen in water, the bottom water of a pond or ditch, exhausted of oxygen, will be replenished only a long time after the surface layers. Hence it will clearly benefit those aerobic or semi-anaerobic organisms which live on the bottom, to have a means of escape which will rapidly carry them from a level of oxygen depletion to a level of oxygen plenty. The principal stimulus to form gas-vacuoles in Arcella and similar organisms which live at the bottom of ponds and ditches, is lack of oxygen. There may be, and probably are, other sets of external conditions which stimulate the production of gas by these organisms, and there are also conditions arising within the cell which stimulate the gas-forming structures. These will be described and discussed later…

It is evident that in Cambridge Bles was well known and respected. Sir Frederick Gowland Hopkins (1861-1947) wrote Bles’s obituary for Nature while he and David Keilin (1887-1963) completed the Arcella paper, the biochemical aspects of which fell into their own interests in cell metabolism.

Hopkins began the obituary in Nature:

By the recent death of Edward J. Bles, zoological science has lost a devoted worker whose qualities of mind and character were of the highest. It is the faith of many of his friends that, but for factors of temperament, and health, he would have become a leader of thought in the subject of his choice. His publications, though of high merit, were relatively few; but his intimates know that they were far from representing all that he accomplished, and are aware of the temperamental restraints but for which he could and would have published much more. He was one of those investigators-deserving sympathy from colleagues with easier standards—who would fain allow publication to wait for perfection, and yet realise even better than others that perfection never arrives. In spite of such inhibitions, or perhaps because of them, his published output is of high value and stamped with the quality of absolute reliability.      For elementary teaching, or, at any rate, for the shackles of departmental teaching and organisation, Bles had some distaste. On the other hand, he was the ideal colleague and one of the most educative influences for the young research worker…

He ended:

Bles was not merely a scholarly biologist in a very wide sense, he was also a man of fine general culture; music, literature, and the arts all made a vivid appeal to him. He had, moreover, a true sense of values and a very beautiful appreciation of the relative importance of things. His knowledge was of the widest, but so philosophic was the cast of his mind that synthetic thought was essential to him. He endeavoured always to see things as a whole. 

I have tried to draw up a list of Bles’s publications; it is shown below.

Bles’s legacy extends beyond his publications. He left the entire residue of his estate (about £44,000) plus his equipment and books to the University of Cambridge. It is difficult to equate the worth of that amount of money to today’s economy but in terms of income value (using GDP/capita as the index) it represents £13 million. Over the years, the Bles Fund has funded the Charles Darwin Chair of Animal Embryology—Bles’s express wish as was its use for ‘the promotion and furtherance of biology as a pure science’.

I have been unable to find a photograph of Edward Bles.

In the final part of this series I will return to Bles’s interest in amphibians and how he came to have a walk-on part in the Kammerer controversy.

Hopkins FG. 1926. Dr Edward J. Bles. Nature 118, 90-91.

Publication by Edward J. Bles (Jeremiah Edward Bles):

Bles EJ. 1884. The remarkable sunsets. Nature 29, 427-428.

Marshall AM, Bles EJ. 1890. The Development of the Kidneys and Fat Bodies in the Frog. Studies from the Biological Laboratories of Owens College 2,133-158 plus 1 plate.

Marshall AM, Bles EJ. 1890. The Development of the Blood-Vessels in the Frog. Studies from the Biological Laboratories of Owens College 2,185-268 plus 3 plates.

Bles EJ. 1892. Notes on the plankton observed at Plymouth during June, July, August and September 1892. Journal of the Marine Biological Association of the United Kingdom 2, 340-343.

Bles EJ. 1893. Director’s Report,—No. I. Journal of the Marine Biological Association of the United Kingdom 3, ix-x.

Bles EJ. 1894. Director’s Report,—No. II. Journal of the Marine Biological Association of the United Kingdom 3, xvii-xx.

Bles EJ. 1898. The correlated distribution of abdominal pores and nephrostomes in fishes. Journal of Anatomy and Physiology 32, 484-512.

Bles EJ. 1898. On the openings in the wall of the body-cavity of vertebrates. Proceedings of the Royal Society 62, 232-247.

Bles EJ. 1901. On the breeding habits of Xenopus laevis Daud. Proceedings of the Cambridge Philosophical Society 11, 220-222.

Bles EJ. 1905. The life-history of Xenopus laevis Daud. Transactions of the Royal Society of Edinburgh 41, 789-821.

Bles EJ. 1905. Notes on the development of Phyllomedusa hypochondrialis. Report of the 74th Meeting of the British Association for the Advancement of Science in 1904, pp 605-606.

Bles EJ. 1905. Bles E J On the hatching of anuran tadpoles and the function…[incomplete]. 6th International Congress of Zoology, Bern 1904. (Compte-rendu des séances du sixième Congrès international de zoologie, tenu à Berne du 14 au 16 août 1904[no further details]

Bles EJ. 1906. The life-history of Xenopus laevis Daud. DSc Thesis, University of London.

Bles EJ. 1907. Notes on anuran development: Paludicola, Hemisus and Phyllomedusa. In The Work of John Samuel Budgett, Balfour Student of the University of Cambridge. Edited by J. Graham Kerr, pp 443-458 plus 6 plates. Cambridge University Press.

Bles, EJ. 1929. Arcella. a study in cell physiology. Quarterly Journal of Microscopical Science 72, 527-648.

Sunday 21 June 2020

Edward Bles, Part 1. Glasgow Winters and Xenopus Frogs

During the latter half of the 20th century African Clawed Frogs (Xenopus) became a major organism for research in developmental biology. They became widely used because for decades they were used for human pregnancy tests. Their use and their spread through hospital laboratories over the world depended on their reliability in responding to the injection of gonadotrophic hormones by laying eggs. The urine of pregnant women contains human chorionic gonadotrophin and the Xenopus pregnancy test became the best biological test before immunological tests were developed. Because they were so widespread and freely available, eggs and embryos for research could be obtained throughout the year by a simple injection in both females and males.

Before any of this was known or put into practice Xenopus and their embryos were studied after natural breeding of Xenopus in captivity. In the wild in South Africa, their breeding behaviour had been described in 1890. Live Xenopus laevis were coming into Britain from South Africa and were being kept successfully, often living for many years, by herpetologists in zoos and in private collection. For example, when Hans Gadow wrote his book in 1901 George Albert Boulenger of the Natural History Museum had kept some in his room in London for at least 11 years. Getting them to spawn though was a different matter. Boulenger’s were seen in amplexus but eggs never appeared.

The first recorded breeding of Xenopus in captivity appears to have been at London Zoo in 1893. The events and development of the resulting tadpoles were described by the Zoological Society’s prosector, Frank Evers Beddard (1858-1925). Eggs were laid in the evening of Saturday 27 May 1893; by Monday 30th they had hatched. It would seem that some were reared to metamorphosis since 5 were admitted to the Zoo’s books on 30 December.

Xenopus tadpole (from Beddard's paper)

Twenty-one specimens of Xenopus had arrived in London Zoo in 1890-93 from several collectors. Beddard states in his paper that those which bred were collected by Frank Finn (1868-1932) in Zanzibar. I will return to this point.

The person associated with first devising a system for breeding Xenopus and in describing their development is Edward J. Bles. In Cambridge Bles was keeping Xenopus but only when a pair was moved into the tropical tank at Cambridge Botanic Gardens did spawning occur. That was in February 1899.

It was while Bles was working in Glasgow that he developed an apparently reliable method for breeding Xenopus although it seems that the female which bred was the same one as in Cambridge. By mid-1903 he was not short of material for embryology. Between April and July 1903 around 15,000 eggs were obtained.

Bles considered it essential that the frogs should be allowed to hibernate. It is easy to forget just how difficult it was in buildings without central heating or electricity to keep tropical aquatic animals warm or to arrange for seasonal changes. In Bles’s time at the University of Glasgow, the zoology department occupied the dark basements and cellars below the Hunterian Museum. To house his frogs, Bles used an arrangement of an inverted bell jar held over a galvanized iron water bath heated from below by a gas micro-burner made by Zeiss. It had been devised by his friend in Cambridge, John Samuel Budgett (1872-1904), a fellow amphibian expert, for keeping tropical fish as well as aquatic frogs. Bles kept the summer temperature at around 25°C but in winter the water in the bell jar was kept at 15-16°C by day, falling to 5-8° at night.

Bles's aquarium for Xenopus

Bles made the point that with a number of amphibians, hibernation appeared essential for the induction of breeding. However, he also arranged for water to be sprayed back into the inverted bell jar aquarium after cooling so as to simulate falling rain. Both these ‘tricks’ are still used to induce frogs and toads to breed.

Bles wrote a long and detailed account of the development of Xenopus, beautifully illustrated by A. Kirkpatrick Maxwell (1884-1975). Bles had been introduced to Maxwell by a friend in Glasgow. It was a lucky break for Maxwell; he was apprenticed to a lithographer and attending classes at the Glasgow School of Art. After his work for Bles  he went on to have an highly successful career as a medical illustrator for the army in the First World War, for example; his drawings were a major improvement for Gray’s Anatomy and he contributed to many other textbooks and journals. His fame extended into the age of molecular biology. Max Perutz commissioned him to draw the model of the haemoglobin molecule.

One of Kirkpatrick Maxwell's plates for Bles
There was an overlay of tracing paper with the lettering

At this stage I must point out that the breeding of Xenopus at London Zoo in 1893 and by Bles in Cambridge and Glasgow between 1899 and 1903 could not have been the same species. All were described at the time as belonging to the species, Xenopus laevis, the Smooth Clawed Frog, and nobody I have found has questioned that assignation. However, the Xenopus aficianados who are reading this article will realise that X. laevis does not occur in Zanzibar. Therefore, and assuming that Beddard had correctly identified the pair collected by Frank Finn, London Zoo bred Müller’s Clawed Frog, Xenopus muelleri (first described by Peters in 1844) which does occur in Zanzibar. Bles states that his animals, two males and two females, came from dealer who had had them for two years. Their previous history was unknown. However, Bles did note that in his frogs the surviving basal portion of the tentacle was very short—a characteristic of X. laevis. By contrast, the tentacle of X. muelleri is as long as the diameter of the eye. Therefore, I think it is safe to assume that Beddard described the breeding and development of X. muelleri while Bles worked on X. laevis. The point is important since the methods described by Bles for X. laevis might not—indeed probably would not—apply to X. muelleri. It is difficult to imagine frogs from Zanzibar, where temperatures range from 20 to 33°C, tolerating a period of hibernation.

Dr Frederic Lionel Vanderkamp (1914-1993) who later became well-known for his research on tsetse flies appears to have been employed in some capacity at Bristol Zoo in the mid-1930s. He wrote an article in The Aquarist magazine questioning whether Bles had failed to discover the real reason for his successful breeding of X. laevis:

…although numerous other zoologists carried out un every detail his methods…they were unsuccessful. The reason, no doubt, was that Bles carried out most of his work at Glasgow where the water is naturally soft (pH about 6.7), whilst other zoologists repeated his methods in their own districts where the pH value of the water was above 7.
It has been discovered, during course of experiment, that X. laevis will spawn, providing they are in fit condition, any time when the pH of their water is lowered under 7. In April 1934, when this species was first bred at Bristol Zoo, they spawned 12 hours after the pH of the water had been lowered, although previously they had been kept seven years together without attempting to mate. Again in December 1934, X. laevis mated about 12 hours after they had been placed in water in which the pH was under 7, similarly again during March this year. Try as we may, we have, so far, failed to get them to mate by any other method except lowering the pH of their surrounding water. It is probable that the Clawed Frog is unable to spawn in alkaline water.

It is difficult to square Vanderplank’s last statement with Bles’s first spawning of X. laevis in Cambridge where the water is hard and alkaline unless for some reason the water in the water lily tank in which they bred had been treated. Similarly, Dr Edward Elkan in his extensive work on the Xenopus pregnancy test in Britain had X. laevis breed in outdoor tanks in London, again not known for having soft, acidic water. In the wild X. laevis is known to breed in acid and alkaline, soft and hard water. I suspect that both Bles and Vanderplank had found that a sudden change in the environment, like water simulating rain, or a shift in pH, also like adding rain water, can be the trigger for reproduction in otherwise quiescent amphibians in captivity. The nature of the change often does not matter, just a change will do.

The observations and descriptions Bles made from fertilization to after metamorphosis have stood the test of time. For example, he showed that the tadpoles within two hours of starting to feed rise to the surface in order to fill their lungs (see my previous post on this topic here). He reasoned that air in the lungs fulfils not only a hydrostatic function but also a respiratory one since in warm water (which holds less oxygen) the tadpoles came to the surface for air more frequently. A similar increase in frequency was seen when the tadpoles were kept in a smaller volume of water, which would lead to hypoxic conditions. He also established that Xenopus tadpoles are suspension feeders, eating microorganisms and other small particles in the water; unlike the tadpoles of the typical frogs they do not scrape surfaces for food.

Bles’s major paper on Xenopus was regarded as a particularly fine piece of work, both by his contemporaries and by those reading it over a hundred years after its publication.

Kirkpatrick Maxwell's depiction of Xenopus tadpoles for Bles

Beddard FE. 1894. Notes upon the tadpole of Xenopus laevis (Dactylethra capensis). Proceedings of the Zoological Society of London 1894,101-107. 

Bles EJ. 1901. On the breeding habits of Xenopus laevis Daud. Proceedings of the Cambbridge Philosophical Society 11, 220-222.

Bles EJ. 1905. The life-history of Xenopus laevis Daud. Transactions of the Royal Society of Edinburgh 41, 789-821. 

Elkan ER. 1938. The Xenopus pregnancy test. British Medical Journal 2, 1253-1256. 

Vanderplanck FL. 1935. The effects of pH on breeding. Aquarist (May-June 1935), 135-136.
For further reading on the history of Xenopus frogs in research, this article contains all the key references:
Gurdon JB, Hopwood N. 2000. The introduction of Xenopus laevis into developmental biology: of empire, pregnancy testing and ribosomal genes. International Journal of Developmental Biology 44, 43-50.

Monday 8 June 2020

Comparative anatomy and physiology of excitatory conduction in the heart: Francis Davies and Eric Francis in Sheffield

‘Have you ever tied a Stannius ligature?’, is a conversation stopper. If the answer is ‘yes’ then you know the person you are talking to studied physiology at some time in the past and that a practical class was concerned with the workings of the frog’s heart—an organ ideal for hamfisted students since it beats spontaneously in isolation and they can learn a great deal about how hearts work in a couple of hours*. However, amphibian and reptilian hearts differ in a number of respects from those of birds and mammals.

One of the key players in the comparative anatomy and physiology of the heart is not remembered by the herpetologists, for example, although his great friend and collaborator is. Francis Davies (1897-1965) was at first sight a classical human anatomist—indeed he became co-editor of Gray’s Anatomy. He was born at Merthyr Tydfil, studied medicine in Cardiff and then University College London. In 1924 he became Senior Demonstrator in anatomy at UCl; he then moved to King’s College London as Reader. In 1935 he arrived in Sheffield as Professor; there he stayed until retirement in 1962. In Sheffield Davies worked on the heart with his friend, Eric Thomas Brazil Francis (1900-1993) who became Reader in Zoology until he retired in 1965.

Together, Davies and Francis studied the hearts of amphibians and reptiles in order to determine how the signal from the pacemaker that sets the heart rate passes first to the atria and then to the ventricle (single in amphibians and most reptiles) or ventricles (in crocodiles as in birds and mammals). Earlier in the 20th century Sir Thomas Lewis (1881-1945) had worked out what happened in mammals: specialised heart muscle cells form a dividing bundle of fibres (the Bundle of His) that convey the message to contract to all parts of the ventricles from the atrio-ventricular node. However, there are no special fibres from the pacemaking sino-atrial node to the atrio-ventricular node; impulses pass across the atria from muscle cell to muscle cell like a Mexican wave. It was Lewis’s brilliant work which made not only the physiology textbooks; the research explained a number of conditions that account for heart disease.

Conduction in the mammalian heart
The structures shown in BLACK are not present in
amphibians and reptiles.
from my 1961 edition of the classical physiology textbook

Francis had already published his book, The Anatomy of the Salamander, and their first joint work, published in 1941, was on the heart of that species (Salamandra salamandra). Francis and Davies concluded that in amphibians and reptiles there is no special conducting system in the heart responsible for spreading the process of excitation to the ventricles; the waves of excitation pass directly but relatively slowly from heart muscle cell to heart muscle cell. In other words, the Mexican wave of contraction continues across the whole heart in contrast to birds and mammals where a specialised bundle of fibres takes over.

Davies and Francis proposed that the reason for this major difference in the heart between ectothermic amphibians and reptiles, on the one hand, and endothermic birds and mammals on the other, is the the pace of life; heart rates are lower in the former than in the latter. Relying on a Mexican wave is just too slow for high heart rates to be achieved. They also suggested that the development of a special conducting system was a relatively recent evolutionary change. Their views still hold good.

But what about crocodilians with their two ventricles? Do they have a system like that in birds and mammals, or one characteristic of extant reptiles? Davies and Francis had that covered. They showed that crocodilians have no specialised conducting pathways.

Francis Davies and Eric Francis were not exemplars of the dyed-in-the-wool anatomists who never lifted their eyes from the dissecting table; nor did they confine their studies to comparative anatomy. Both stressed form and function. Davies while undoubtedly seen as a human anatomist of the old school, stressed in teaching anatomy to medical students ‘living’ functional anatomy. Francis was a zoological polymath. In their work on the vertebrate heart, they threw every technique then available at the problem of how excitation by the pacemaker is conducted to all parts: gross observation, dissection, serial sections for histology, histochemistry, slow-motion cinephotography, in-vitro physiology and electrocardiography.
Francis Davies had been unwell for some years when when he retired in 1962. He died in 1965. Eric Francis wrote his obituary for the Journal of Anatomy.

ETB Francis's drawing of the Salamander heart from the 1941 paper

*By tying two ligatures Hermann Friedrich Stannius (1808-1883) showed that the pacemaker of the frog’s heartbeat is in the sinus venosus and that impulses pass from there to the atria and then the ventricle. By isolating regions of the heart these two ligatures also showed that the chambers beat to their own rhythm spontaneously in the absence of input from the pacemaker. The first Stannius ligature is tied between the sinus venosus and the right atrium; the second between the atria and the ventricles. As a hoax the late Jim Linzell and I, in response to a letter asking for exhibits for a museum, put a length of cotton thread in an envelope and sent it along with the explanation that this was Stannius’s third ligature which he never got round to using because his wife had sent a message telling him to get home before his dinner got cold. It was dated 1 April. We never had a reply.

Davies F, Francis ETB. 1941. The heart of the salamander (Salamandra salamandra L.), with special reference to the conducting (connecting) system and its bearing on the phylogeny of  the conducting systems of mammalian and avian hearts. Philosophical Transactions of the Royal Society B 232, 99-130.

Davies F, Francis ETB. 1946. The conducting system of the vertebrate heart. Biological Reviews 21, 173-188

Davies F, Francis ETB, King TS. 1951. Electrocardiogram of the crocodilian heart. Nature 167, 146.

Davies F, Francis ETB, King TS. 1952. The conducting (connecting) system of the crocodilian heart. Journal of Anatomy 86, 152-161.

Francis, ETB. 1965. In memoriam: Francis Davies. Journal of Anatomy 99, 913-915.

Jensen B, Boukens BJD, Postma AV, Gunst QD, van den Hoff MJB, Moorman AFM, Wang T, Christoffels VM. 2012. Identifying the evolutionary building blocks of the cardiac conduction system. PLoS ONE 7(9): e44231. doi:10.1371/journal.pone.0044231 

Tuesday 2 June 2020

Vole Population Crashes: Was there an attempt to suppress a ‘lamarckian’ hypothesis in the 1950s?

Field Vole or Short-tailed Vole
Photograph by Tim Melling

I apologise in advance for this post. In trying to find the answer to an allegation that a paper was suppressed because it proposed a controversial hypothesis, I have to skim the surface of a topic at the heart of ecology. It is a topic that has spilt over into the physiology of ‘stress’ and it is a topic that has been the subject of a great deal of mathematical modelling. I am dealing with just one aspect from a mainly historical perspective but it is an aspect that is at the centre of the problem of factors controlling animal populations and one which provoked an often bitter controversy. The question though is simple: how can fluctuations in the size of populations of voles from year to year be explained?

I knew little of the work of the Bureau of Animal Population which existed at Oxford from 1932 until 1967 under the leadership of Charles Elton1. What I did know came first from my former colleague at Babraham, the late John Perry2, who had been a member of the Bureau in the 1940s, and from his friend H.N. ‘Mick’ Southern3, another stalwart, when the three of us sat together at meetings of the old Zoological Club in the 1970s. Another member, John Clarke4, sometimes came to Society for Endocrinology meetings to describe his continuing work on the reproduction of voles. Before that I knew from gossip the battle that went on to bring the Bureau in the zoology department proper because In the mid-1960s interest in the goings on at Oxford was intense. Zoology at Oxford has a well-maintained reputation for internecine warfare and John Phillips5 returned to Hong Kong from a short visit to U.K. in 1966 full of stories he had heard of the troubles at Oxford occasioned by the eventually successful attempts of the head of department, J.W.S. Pringle6, who had arrived from Cambridge in 1961 determined to change things, to integrate the outlying units, into the zoology department.

A couple of years ago I found that Peter Crowcroft7 had written a book on the history of the Bureau, of which he was a former member. As I read it I came across what appeared to be a shocking example of scientific censorship in the early 1950s. I thus became acquainted with the world of voles and of Dennis Chitty8 who, after Oxford, was Professor of Zoology in the University of British Columbia. This is what Crowcroft wrote:

When Chitty had analyzed his data from the Lake Vyrnwy population [of the Field Vole, Microtus agrestis] that had been stud­ied continuously from 1936 through 1939, he found himself unable to explain their crash in terms of the classic factors: food, weather, preda­tion, and disease. He came to suppose that overcrowding and its asso­ciated social strife might have caused the high mortality among young voles born when numbers were highest. Adverse effects of overcrowding could also explain the reduced productivity of females subjected to it. That hypothesis would not have caused any raised eyebrows, even in the 1940s. The Lake Vymwy population continued to decline, however, in the next generation, when there was no longer an overcrowded vole society, and when food appeared to be abundant. Chitty felt obliged to offer, as the simplest possible explanation, the existence of an inherited disability: "During the time of their almost complete disappearance in 1938 or 1939 voles were not subjected to any known environmental conditions likely to have caused excessive mortality. The hypothesis is therefore advanced that death was primarily due to adverse conditions to which the parents were subjected in the previous breeding season."       
That suggestion not only caused the eyebrows of authorities in popu­lation matters to go up, it also raised the hairs on the backs of their necks. This smacked of the Lamarckian heresy! Chitty could not get the paper published in the journal of his choice. But Sir Alister Hardy read it objectively, and communicated it to the Royal Society for publication in their Transactions, a most prestigious place. 

Now ‘maternal effects’—an example of which Chitty proposed—are well-known phenomena in many different organisms. They are lamarckian in the sense that a mother (or a father through ‘paternal effects’) can affect the performance of her offspring by pathways not involving a difference in the genes (which would be really lamarckian). Maternal effects, in short, are a form of non-genetic inheritance†.

If what Crowcroft wrote was true, the editors of the journal to which Chitty’s paper was first submitted would indeed have been guilty of suppressing an inconvenient hypothesis. However, Crowcroft made several mistakes in describing Chitty’s work which made me wonder if he had got hold of the wrong end of the stick. The first error was that Sir Alister Hardy did not communicate the paper for publication by the Royal Society. The Fellow who did was the then Professor Peter Medawar9. The second was that Crowcroft seemed to confuse this hypothesis of Chitty’s, which involved a maternal effect, with his later hypothesis for the phenomenon of vole cycles which involved genetic selection at different stages of the population cycle. This replacement hypothesis, not the one for a maternal effect, has been termed the ‘Chitty Hypothesis’.

After I read this Crowcroft’s account I began to think that Chitty and the people around his lab (including Crowcroft) had interpreted rejection of his paper because the hypothesis he advanced to explain it was lamarckian, rather than for the multitude of other reasons editors reject papers or suggest parts be rewritten. Crowcroft’s book appeared in 1991. In 1996 Chitty himself wrote a book describing his virtually lifelong interest in the control of animal populations and the disappointments it had caused him.  Chitty made no mention of the paper being rejected because it contained an apparently lamarckian hypothesis but because he had dared to propose a hypothesis at all. He wrote of this episode:

The account of my prewar work would have appeared in the Journal of Ani­mal Ecology if Charles [Elton] and I had not stepped down as editors. But the new editor, H.C. Gilson, took a dim view of the paper and wanted it rewritten. Ten of the pages, he complained, seemed to be largely speculation. “Even if they were not, [he wrote] they would be too general in character to hang on to this paper.” His comments confirmed the doubts I held at the time about the danger of speculating, especially as they were followed by phases such as the following: “All this is mere vague speculation . . . these ex-cathedra statements . . . if you will read the paper critically . . . infuriating to the reader . . . would you make up your mind . . . such indifferent photographs . . . much of interest and value pokes out of the paper like gleams of sun­ shine in places.” 
     I was more than somewhat upset—more than I should have been…This is probably the way most young authors feel when one of their brainchilden has been thrown to the lions of peer review. So it was some time before I could look objectively at the contrast between what I’d writ­ten—“needless to say I shall very gratefully welcome all your criticisms”— and the lack of gratitude I felt when they landed on my desk. 

In short there seemed to be no mention of a particular hypothesis, only that the data did not justify the degree of speculation. Chitty went on to describe the rôle of Medawar in getting the paper published: ‘His opinion of the need to speculate (though not necessarily of how I did it) restored my self-confidence’.

The question remains: would Chitty’s paper rewritten on the lines suggested by the editor of Journal of Animal Ecology have made a better paper than that which appeared largely unchanged in Philosophical Transactions of the Royal Society. I thought I, a non-ecologist, should read it.  And so I did, several times, and found my sympathies lie, 70 years on, with the editor of Journal of Animal Ecology. The style of data presentation alone has changed greatly but even so the paper would have qualified for my late colleague’s description of ‘publishing the contents of his notebook’. However, ‘much of interest and value pokes out of the paper like gleams of sun­ shine in places’ as Gilson wrote. Perhaps Chitty should have grasped the nettle and re-written it in a less discursive style while aggregating the raw data into simpler tables with more statistical analysis. My guess is that Gilson*, as the new editor of Journal of Animal Ecology, was attempting to present ecology as a harder science with crisp analysis and presentation than that conveyed by the previous Elton/Chitty régime.

A fierce critic of Chitty’s interpretation of the data from Lake Vyrnwy was David Lack10, next door at the Edward Grey Institute of Field Ornithology. Lack was of the view that only three factors can control natural populations: disease; predators or parasites; food shortage. He did not accept that Chitty had eliminated the influence of these factors before producing a hypothesis that crowding and thus ‘strife’—in other words control entirely within the vole population itself—causes the fall in numbers. While Chitty defended his views vigorously, on reading his book I remained unconvinced that he had eliminated the rôle of ground predators like stoats and weasels or that tuberculosis, which was present, might have been more important in the population declines than the evidence then suggested.

If, on the other hand, the external factors of Lack really can be eliminated as an explanation, which Chitty continued to contend, and having read something of the recent thinking on explanations of cycles in vole populations, there seems to be the view that Chitty’s original idea of maternal effects brought on by crowding might provide the answer rather than his ‘Chitty Hypothesis’ based on changes in selection and gene frequency.

In conclusion, I have not been able to confirm Crowcroft’s view that Chitty’s paper was rejected by the editor of Journal of Animal Ecology because it ‘smacked of the lamarckian heresy’. It is true that rejection on those grounds could have been hidden in the criticism of ‘speculation’ but having read the paper I can see why the editor acted as he did; he may not have objected to a particular hypothesis but to any hypothesis being advanced from what he, or possibly a referee advising him, saw as incomplete or inadequate data.

Finally, Lake Vrnwy, an artificial reservoir in North Wales which supplies Liverpool with tap water, is well-known to those who watch Springwatch on BBC television. The surrounding land is managed by the RSPB and in case any readers wonder where exactly the vole surveys of the late 1930s were done, I have drawn them on the map produced for visitors to the reserve. The habitat is though probably not suitable for Field Voles. At the time of the studies trees had been planted for forestry but the open nature of the ground remained vole friendly. That is probably not the case now but never having been to Lake Vrnwy I do not know.

The RSPB current map with the study areas from the 1930s marked in RED


After reading about vole cycles and the lack of any settled view on their cause I was left feeling that a long-term study should be done in a suitable habitat, applying all the knowledge of how to do such research that has accumulated over 80 years. While the same areas around Lake Vrnwy may not be suitable, why not repeat the studies elsewhere?

Dennis Chitty
from obituary by Charles J Krebs
for the
Royal Society of Canada

from Acta Theriologica 42, 1997

*The editor was Hugh Cary Gilson (1910-2000) a freshwater biologist who from 1946 to 1973 was Director of the Freshwater Biological Association.

†A good definition of maternal effects was provided by Mather & Jinks in 1970: Maternal effects arise where the mother makes a contribution to the phenotype of her progeny over and above that which results from the genes she contributes to the zygote. 

1.Charles Sutherland Elton FRS, 1900-1991
2.John Sherwood Perry, 1917-2010
3.Henry Neville "Mick" Southern, 1908-1986
4.John Rigarlsford Clarke, ca 1925-2010
5.John Guest Phillips FRS, 1933-1987
6.John William Sutton Pringle FRS, 1912-1982
7.William Peter Crowcroft, 1922-1996
8.Dennis Hubert Chitty, 1912-2010
9.Peter Brian Medawar OM FRS, 1915-1987
10.David Lambert Lack FRS, 1910-1973

Chitty D. 1952. Mortality among voles (Microtus agrestis) at Lake Vrynwy, Montgomeryshire in 1936-9. Philosophical Transactions of the Royal Society B 236, 505-552.

Chitty D. 1996. Do Lemmings Commit Suicide. New York: Oxford University Press.

Crowcroft P. 1991. Elton’s Ecologists. Chicago: University of Chicago Press.