SPAWNING BEHAVIOR IN FUNDULUS HETEROCLITUS. 315 



The wash drawings reproduced in Plates XXVII. and XXVIII. 

 were made under my direction by Miss Ella Weeks of the State 

 Agricultural College of Kansas. I take this opportunity of express- 

 ing my appreciation of the quality of her work and my indebted- 

 ness to her for her service. I also wish to express my thanks to 

 Professor Jacob Reighard for his helpful suggestions and criticism. 



The plan of the paper is to treat each species separately, to 

 give a summary of the main points, and to conclude with a gen- 

 eral discussion of the origin and significance of the structure and 

 behavior described. 



The four species dealt with all belong to the family Pceciliidae 

 (the killifishes). The following statements referring to sexual 

 dimorphism in this family are quoted : 



" Sexes usually unlike, the fins being largest in the males, but in some 

 species the females are much larger in size. Many of the species are 

 ovoviviparous, the young well developed at time of birth. In these species 

 the sexes are very unlike, the anal fin of the male being developed into an 

 intromittent organ." -Jordan and Evermann, "Fishes of North Amer- 

 ica," p. 631. 



"In many species the sexes are dissimilar, the female being larger and 

 less brilliantly colored, with smaller fins. " " Cambridge Natural History. 



I have been unable to find anything in the literature concerning 

 the spawning behavior of these species. 



For purposes of clearness it seems best to present the facts on 

 spawning behavior before those on sexual dimorphism, since 

 behavior throws so much light on the significance of structures. 



FUNDULUS HETEROCLITUS (Linn.). 



(Common Killifish ; Mudfish; Cobbler; Mud Dabbler ; 



Mummichog.) 



Spawning Behavior. 



The spawning act proper was the first to gain my attention and 

 it is hardly likely that I should have noticed it had I not been 

 slightly familiar with Professor Jacob Reighard's unpublished 

 observations on the spawning habits of certain inland species. 

 In spawning the male clasps the female firmly around the slender 

 portion of the body just back of the dorsal and anal fins, using 

 as claspers his large, strong anal and dorsal fins. The two fins 



