CONTACT ORGANS IN KILLIFISHES OF WOODS HOLE. 



1/3 



In all species the contact organs occur on the top of the head 

 and upon the snout, places where there is little or no direct contact 

 in spawning proper. These regions, however, are used constantly 

 as contact surfaces during courtship and rivalry. During court- 

 ship the male swims beneath the female and seems to guide her 

 about from place to place by gently "butting" her with the top 

 or sides of the head. Rivalry in at least two of the species, F. 

 heteroclitus and Cyprinodon variegatits, is very intense. Two 

 males rush at one another head on and strike one another 

 savagely with cheeks, jaws and snouts. Such contests may be 



6 



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

 fins of spawning males. 



FIG. 5- Fundulus heteroclitus, X 1 6. 



FIG. 6. F. diaphanus, X J 6. 



FIG. 7. Enlarged detail drawing of a portion of the exposed margin of a scale 

 tajien 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 in the non-calcified portion of the 

 scale, X 3- 



kept up at intervals for days. A number of specimens were ex- 

 amined after they had been engaged in combat for some time to 

 determine the effect of fighting upon the contact organs. In all 

 cases the latter were found to be much worn, many showing the 

 supporting spike stripped of dermis and epidermis. Apart from 



