3o6 THE BIOLOGY OF THE FROG chap. 



a number of frogs of both sexes are placed together during 

 the breeding season, the males will be found to be clasping 

 females instead of other males. The question naturally 

 arises : How does the male frog distinguish the female 

 from one of his own sex? That it is not, as in many 

 animals, through the sense of smell, was shown by Goltz 

 by cutting through the olfactory lobes of several male 

 specimens; after this operation the mutilated males were 

 placed among several females, and in a short time they were 

 all in copulation with members of the other sex. Then 

 several males which were blinded were placed among the 

 females, with the same result as before. That it is not the 

 sound produced by the female that reveals her sex, was 

 shown by Goltz by placing several females, which had been 

 rendered incapable of using their voice, among the males. 

 These were as readily seized as normal females. After the 

 destruction of both smell and sight, males were found to 

 be still able to distinguish the females, although there was 

 apparently a certain diminution of their ardor. The senses 

 of sight, smell, and hearing are not, therefore, the exclusive 

 or indispensable means of sex recognition, whatever be the 

 part they play under normal conditions. Neither are the 

 higher nerve centers necessary. Goltz cut through the skull 

 of a male so as to cut off the cerebral hemispheres and 

 eyes ; the specimen almost immediately clasped a female that 

 was presented to it, while a male that was offered was rejected. 

 The form of the body differs in the two sexes, especially 

 when the female carries a large mass of eggs, but this alone 

 does not enable the male to distinguish the female. Goltz 

 found that if the bodies of males were filled with flesh and 

 sewed up so as to resemble the form of the females, they 

 would be clasped for a short time and then rejected. The 

 bodies of freshly killed females, on the other hand, were 



