The Recognition of Sex 231 



modes of behavior not observed in the female. It 

 appears, then, that the brilliant fish distinguishes the 

 two by their behavior; a mode of sex recognition 

 pointed out by Holmes ( 1903) in the case of amphi- 

 pods. In the case of very young males the sex recog- 

 nition must be wholly of this character, while males 

 which already show some little sexual coloration are 

 probably distinguished upon near approach by means 

 of it as well as by behavior." ^ 



Among the amphibians the recognition of sex in 

 the frog has been the subject of several interesting 

 experiments by Goltz. In frogs and toads the males 

 clasp the females during the breeding season until 

 the eggs are discharged when the male sheds his 

 sperm over them. What it is that induces the male 

 to discharge his sperm at the opportune moment 

 when the eggs are passing from the female has never 

 been satisfactorily cleared up. The clasping of frogs 

 insures that the male is on hand when his services 

 in fertilizing the eggs are required. The clasping 

 instinct is a temporary one, coming on early in the 

 spring, and then ceasing after the short breeding 

 period is past, when the sexes scatter and pay no 

 further heed to one another's existence. As is well 

 known, male frogs and toads often clasp various 

 objects during the breeding season. Frogs have been 

 found to clasp fishes the eyes of which they some- 

 times gouge out with their thumbs ; and I have taken 

 a male toad industriously clasping an old dried apple. 



^Biological Bulletin. Vol. 14, p. 35, 1907. 



