MATING BEHAVIOR OF THE WOOD FROG. 183 



rapidity of the movements suggested to the observer that 

 possibly sex-recognition may have become complete at this dis- 

 tance before the male moved. No similarly vigorous attack upon 

 a quiet male was observed though at times part of the pond 

 contained a male frog for almost every square foot of surface. 



Dead females are distinguished from dead males. 



The readiness with which the attempt of a male to pair with 

 another male is given up on near approach, the keenness of the 

 male's pursuit after once approaching very near or touching a 

 female, and the discrimination between a dead male and a dead 

 female particularly in cases in which, to the human eye, the latter 

 is indistinguishable in size, color and general features from a 

 male, suggest that a chemical sense iv( involved in final sex- 

 recognition though one experiment designed to test this hy- 

 pothesis was unsuccessful. 



The writer regrets his inability to further pursue the subject 

 experimentally, but the pressure of other work left no opportunity 

 to work on the problem during the height of the breeding season 

 in 1913 and such will probably be the case in future seasons. 



