182 Mr. G. A. Boulenger on 
There is another criticism—one of the most important— 
which Kammerer has not yet answered. ; 
Having bred the “ water-form ” to a fourth generation, this 
is what he claims to have observed :— 
“Es zeigt sich aber an den geschlechtsreifen Mainnchen 
vierter Generation eine weitere morphologische Variation... 
waren die briinftig gewordenen Manncehen alle mit schwarzen 
verfiirbten Schwielen an der Oberseite des Daumens und am 
Daumenballen versehen und ebenso zeigt sich an ihnen eine 
Hypertrophie der Vorderarmmuskulatur ” (2, p. 516, fig. 26). 
When I first saw the figure of the male Adytes with black 
nuptial callosities on the “ Daumen” or inner finger I con- 
cluded that such a disposition was highly improbable, if not 
impossible, basing my opinion on the small size and the 
shape of this finger in normal individuals, and I have since 
satisfied myself, by handling a pair im ampleau, that, if 
callosities should ever develop on the fingers, they would 
be on the two inner fingers, both being in contact with 
the inguinal region of the female—a correlation to which I 
know of no exception. It is true that Kammerer appears to 
_have been under the erroneous impression that the thumb 
lone plays a réle in the amplexus in all European Anura :— 
“ Bekanntlich steigt das Anurenmiinnchen seinem Weibchen 
auf den Riicken und umklammert es, indem es seine Daumen 
bald in die Lenden bald in die Achselgrube des Weibchens 
einstemmt ” (4, p. 100). 
As I told Prof. Bateson at the time, if a specimen such as 
is figured could be produced, I would cease to doubt any of 
Kammerer’s statements. This is how the matter now stands, 
according to Bateson * :— 
“Regarding the Alyées bred in this way ” [alleged atavistic 
reversion to aquatic breeding-habits] ‘“ Kammerer makes the 
very striking statement that the males in the third generation 
have roughened swellings on their thumbs and that in the 
fourth generation these swellings develop black pigment. 
Together with the appearance of this secondary sexual 
character there is hypertrophy of the muscles of the fore arm. 
To my mind this is the critical observation. Ifit can be 
substantiated it would go far towards proving Kammerer’s 
case. Alytes, among toads and frogs, is peculiar in that the 
males do not develop these lumps in the breeding-season, and 
the fact may no doubt be taken to be correlated with the 
breeding-habits, copulation occurring on land, and not in 
* ¢ Problems of Genetics’ (New Haven and London, 1913), p. 201. 
