SPAWNING BEHAVIOR IN FUNDULUS HETEROCLITUS. 



329 



while some of these possess them only on the top or sides of the 

 head. It is my belief, although I am not at present in possession 

 of any direct evidence on the subject, that the organs are developed 

 antero-posteriorly, either in response to a fixed law of develop- 

 ment or because there is an earlier need for these structures on 

 the cheeks and on the top of the head, since these parts are used 

 in the preliminary courtship, coming into frequent contact as 

 they do with the body of the female. 



The contact organs are practically alike in all of the species 

 studied, although they vary slightly in form and in size relative 

 to that of the scale on which they occur. They are best developed 



TEXT PLATE IV. 



Camera drawings of typical scales from the region between the dorsal and anal fins 

 of spawning males. 



1. fundultts heteroclitus. 



2. F. diaphanus. 



3. Enlarged detail drawing of a portion of the exposed margin of a scale taken 

 from the side of a male F. majalis. The black region represents the horny margin 

 of the growing region of the scale that is prolonged into spikes that support the 

 contact organs. The stippled area represents the dermis. The clear outside area 

 represents the epidermis. The striated portion is the non-calcified portion of the scale. 



in Fundtdns, inajalis, but are simply larger here than in the species 

 under consideration. Photographs and camera drawings (see 

 Text Plates III. and IV.) show clearly the appearance of the con- 

 tact organs in typical scales taken from males of the four species. 



