STUDIES IN THE EXPERIMENTAL ANALYSIS OF SEX. 443 
that after the breeding season there is a sadden casting of 
the very large black papillae on the pad, but smaller papillae 
remain below during the early summer months, and are only 
gradually obliterated. It appears, further, that this gradual 
obliteration of the small papillae which takes place in the 
summer is not due to a reduction of the epidermal cells, but 
Text-figs. A, B, and C. 
B. 
Camera drawings of outline of part of the thumb-pad of normal 
male frogs (side view). A. In breeding season. B. After shedding 
pigmented pad. C. Quite smooth, as in July and August. X 67. 
to an increase of them over the whole pad, with the result 
that the spaces between the papillae are filled up and a smooth 
surface is thereby formed. This interpretation — viz. that 
the obliteration of the remains of the papillm during the 
summer is due, not to a reduction, but to an increase of the 
epidermal cells — is based on the fact that sections of the 
