440 
GEOFFREY SMITH AND EDGAR SCHUSTER. 
another, was transplanted into the peritoneal cavity. The 
wound was then sutured together in two layers with cotton, 
and the animal was kept in a zinc box lined with damp moss, 
which was frequently renewed. A supply of small worms 
was given to the frogs, and these were eagerly devoured in 
the summer and early autumn, but during late autumn and 
winter the frogs refused to feed owing, no doubt, to the fact 
that normally during these months the frogs are hibernating 
and do not feed in a state of nature. 
A great difference was observed in the mortality of the 
animals according as they were operated on in the summer 
or autumnal months, the mortality in spring and summer being 
very high, but in late autumn or winter very low. In one 
set of fifteen frogs operated upon in November, the mortality 
was 0 per cent. 
The object of the experiments was to determine the effect 
of ovariotomy and castration upon the development of the 
thumb, which normally exhibits a characteristic pad in 
the male; to discover whether the effects of castration 
in the case of the male could be counterbalanced by the 
transplantation of testes from other frogs, or by the injection 
of testis-extract, and also to observe the fate of the trans- 
planted organs according as they were left in the body of the 
animal to which they properly belonged (auto-transplantation), 
or transferred to the body of another individual, male or 
female (alio- transplantation). 
Before describing the experiments it is desirable to give 
an account of the cyclical changes which take place in the 
testes and the thumb-pads of normal adult male frogs 
(R. fusca) at different times of year. Our own observations 
agree on the whole with those of Nussbaum ( 1 ) and Ploetz ( 2 ), 
but we must add certain facts with regard to the thumb which 
are of essential importance for the interpretation of experi- 
mental results. The testes exhibit their smallest size in March 
or April after the shedding of the spermatozoa at the breeding- 
season. From this period onwards until August they steadily 
increase in size, attaining their full dimensions by the 
