ARTICLES 403 



strings sink to the bottom of the water, and in due time small 

 tadpoles hatch out, each provided with three feather-like gills 

 at the side of the neck. As the tadpoles grow, a fold of skin, 

 termed the operculum, grows back from the head and covers 

 up the gills, and the body of the tadpole then assumes the round 

 plump form familiar to all of us. But Alytes differs from all 

 other toads in the fact that it pairs on land ; and as the skin 

 of the female is comparatively rough and dry, the male does not 

 develop the horny pad on his hand, since he can hold her with- 

 out it. The eggs are much larger than those of ordinary toads, 

 and fewer in number. As they are emitted and fertilised, the 

 male winds the egg-strings round his legs and hops away 

 encumbered with them. Some weeks later he visits the water, 

 and the eggs are hatched ; tadpoles emerge which have already 

 covered up their gills, and resemble the later stages of the 

 tadpoles of other toads. 



Now, Kammerer found that, if Alytes was accustomed to 

 warm drv conditions, it would still flourish if a tank was 

 provided in which the toads could bathe themselves when 

 they so desired. Under these circumstances they begin to 

 pair in the water, and the egg strings become slippery and fall 

 off the male's legs and lie in the water. Most of them perish, but 

 if the water is kept perfectly sterile, a few will survive. These, 

 when they reach maturity, will pair in the water — and the eggs * 

 produced by the female will be much smaller than normal, and 

 more like those of ordinarj^ toads, and the tadpoles will emerge 

 in an earlier stage of development, showing the external gills. 



Of these, however, there will only be one on each side — and 

 only one external gill is found in the embryos of the normal 

 Alytes, if the eggs are opened before hatching. If, however, a 

 third generation of Alytes is raised under these conditions, eggs 

 will be produced from which tadpoles will hatch out showing 

 three external gills on each side as in ordinary toads ; and these 

 eggs when reared will yield males with horny patches on their 

 hands. As such Alytes had never previously been recorded, 

 this point was fixed on by Dr. Bateson, the leading English 

 Mendelian, to test the reliability of Kammerer as an investigator. 

 He visited Kammerer's laboratory and demanded to be shown 

 these abnormal toads, and this wish Kammerer was either un- 

 willing or unable to comply with. Hence Dr. Bateson felt justified 

 in regarding these results with great suspicion ; this was a few 

 years before the war. In 19 19, however, Kammerer published 

 a further paper on the subject, giving the results of renewed 

 experiments. He succeeded in rearing these modified Alytes 

 through six or seven generations, and found that the horny 

 pad increased in size and definiteness up till the fifth generation, 

 after which it remained stationary. He explained his inability 



