Dorothy Sladden (1907-1937): Ernest W. MacBride, Evolution and Eugenics. Part 4. At London Zoo

We know from the council minutes of the Zoological Society that when she died, Dorothy Sladden was working on Proteus anguinus, the cave-dwelling Olm. She must have been trying to see if she could repeat Kammerer’s experiments in which he claimed eyes developed when they were kept under alternating red light and daylight, or, possibly, at  the colour changes when they are kept in the light. Indeed this is what Zoo magazine (later Animal and Zoo Magazine) reported in December 1936 (Volume 1, No. 7, p34):

They Hate the Light
     Six odd little amphibians which never metamorphose into adult air-breathing animals are the most recent arrivals at the Aquarium. They are olms or Proteus, and they live in the perpetual darkness of underground caves and romantic stalactite grottos in Dalmatia and neighbouring countries.
     They are between eight and ten inches long and are quite white and blind, with branching gills which are coloured blood-red. They eat chopped earthworms.
     When exposed to the light they gradually change colour, becoming quite dark. If they are placed in direct sunlight they turn jet black.
     Experiments at the Zoo have shown that they resent the light and become active when it shines upon them, trying to seek a dark corner to escape from it. But a curious fact is that there is a definite time lag of four or five seconds between the first turning on of the light and the beginning of their activity.

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E.W. MacBride had retired in 1934, presumably at the end of the year when he reached 65. He was still active on the Zoo council and must have played a part in obtaining a grant from the old Department of Scientific and Industrial Research (DSIR*) to support her work. It is also clear that she was continuing her work on stick insects up to the time of her death in June 1937, presumably at Imperial College. My estimate is that she moved to the Zoo (where, MacBride reported, she worked in the aquarium) sometime in 1935 since her observations on breeding Angel Fish were made in June1936.

The Zoo aquarium must have been an interesting place. The curator was Edward George Boulenger (1888-1946); he and his father George Albert Boulenger FRS (1858-1937) had examined aspects of Kammerer’s claims and were known not to believe them. E.G. had shown that Kammerer’s salamanders with different colour patterns, which were said to be the result of being kept on substrates of different colour, were more likely to be from different geographical races. So we have Boulenger, clearly not a convinced Lamarckian, an employee at the Zoo, Julian Huxley (not quite then but soon-and-desperate-to-be FRS), as Secretary, and a Darwinian, another employee but as chief executive, at the Zoo and we have Ernest MacBride FRS, arch-Lamarckist and Kammerer’s vicar on earth, a powerful figure on the Zoo Council. In the middle somewhere was Dorothy Sladden.

Angel Fish (from Wikipedia)

From her brief time at the Zoo Dorothy Sladden wrote one scientific paper, The breeding habits of the Angel Fish, Pterophyllum scalare, published in Proceedings of the Zoological Society  (A107, 187-189) published shortly after her death in 1937. She also started to write for the weekly magazine Water Life, first published in 1936. The articles appeared between April and June 1937 and can be seen in full here. Her first article was a reprise of her paper on breeding Angel Fish. It began:

Although the Angel Fish (Pterophyllum scalare) is bred in large quantities un Germany, so far little success has attended the efforts of the experts in this country. In view of this fact, the following notes on the conditions under which these fish were bred at the London Zoo may be of some interest.

Her next article, A Fantastic Toad at the Zoo, described the Escuerzo (Ceratophrys cornuta) given to the Zoo by a Mr J.J. Morris. Then she described British Adders at the Zoo:

The first warm days of spring see the re-stocking of the the Zoo’s outdoor reptiliary. Apart from the hardier species of reptiles imported from Southern Europe and obtained from a dealer, the Zoo relies on the efforts of the snake catcher of the New Forest, who annually catches several hundreds of British adders (Vipera berus) for the Society. Mr George Wateridge, successor to the New Forest’s former snake catcher, the well-known Brush Mills, has already sent thirty Adders to the Zoo…

Finally, she drew attention to A “New” Disease in Tortoises:

Among the many enquiries from pet keepers which have reached the Zoo’s Reptile House recently a large proportion deal with a very infectious disease among Tortoises which leads to blindness. The disease was first noticed in this country in 1935, among some newly imported Greek Tortoises.

I started this story because I came across her name while looking into Burgess Barnett’s departure from the Zoo in 1937. Therefore, while copying the articles she wrote in Water Life, it was fascinating to find that two photographs used to illustrate the articles, both shown here, were taken by Joan Barnett. This must be Burgess Barnett’s daughter, Joan, born in 1917, and then aged 20. My story had come full circle.

That article from the issue of 1 June 1937 was followed in the issue of 29 June by the announcement of her death as the result of a road accident. She had died two days before the date of issue of the magazine. The editor, Margery Elwin, must have been informed very quickly to get the news into print that quickly. Did she know Dorothy Sladden well? They were both about the same age, born in 1907 and 1908, both zoology graduates and both keen animal keepers with connexions to the aquarium at the Zoo. The reason I wonder is that Margery Elwin was, in her articles, sympathetic to Lamarckism but her membership of the Communist Party of Great Britain and the espousal of Lysenko in the years after the War is, perhaps, another explanation.

I have been unable to find any further information on Dorothy Sladden’s fatal accident. There must have been a report on the inquest into her death in a local newspaper but progress at scanning is now being done at such a very slow rate by British Newspaper Archive that I suspect it will be some time until I can find out what happened.

We also do not know whether Dorothy Sladden was a follower of MacBride or, like so many at Imperial College, even those involved with the work itself, openly or quietly dismissive of his attachment to Lamarck and Kammerer.

Finally, a plea for more information. I have been unable to find a photograph of Dorothy Sladden; if anybody has one or can point me in the direction of where I might find one I would be most grateful. I have found her mother and father (but not her) on a public family tree which covers her maternal line. I shall contact the owner, with these posts now complete, to see if there are any surviving cousins who might know more of her history.

As I said at the beginning of Part 1, this is a sad story. I hope I have done her justice in describing her contributions to the debate on how evolution happens that was raging in the early decades of the 20th Century, and have drawn attention to her skills as a zoologist who actually knew a lot about animals, real live animals.

This is her full bibliography (including the articles described above):

Dorothy Ena Sladden

1907-1937

Sladden, D.E. 1930. Experimental distortion of development in amphibian tadpoles. Proceedings of the Royal Society B 106, 318-325

Sladden, D.E. 1932. Experimental distortion of development in amphibian tadpoles. Part II. Proceedings of the Royal Society B 112, 1-12

Sladden, D.E. 1934. Transference of induced food-habit from parent to offspring. Part I. Proceedings of the Royal Society B 114, 441-449

Sladden, D.E. 1935. Transference of induced food-habit from parent to offspring -II. Proceedings of the Royal Society B 119, 31-46

Sladden, D.E. & Hewer, H.R.1938. Transference of induced food-habit from parent to offspring. III. Proceedings of the Royal Society B 126, 30-40

Sladden, D.E. 1937. Angel fish bred at the zoo. Water Life  (13 April 1937) 2, 172

Sladden, D.E. 1937. A fantastic toad at the zoo. Water Life (4 May 1937) 2, 211

Sladden, D.E. 1937. British adders at the zoo. Water Life (11 May 1937) 2, 217

Sladden, D.E. 1937. A “new” disease in tortoises. Water Life (1 June 1937) 2, 269.

Sladden, D.E. 1937. The breeding habits of the Angel Fish, Pterophyllum scalare. Proceedings of the Zoological Society of London  A107, 187-189

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*DSIR was abolished in 1965, its major function of supporting research in UK being taken over by the Science Research Council (SRC) under the Science and Technology Act. I applied to DSIR in 1965 and my grant to go to Hong Kong came from SRC.

UPDATED: 16 June 2019