SPAWNING BEHAVIOR IN FUNDULUS HETEROCLITUS. 33! 



tive families such as the one with which we are dealing. Is it 

 not possible that we have in this family ctenoid scales developed 

 as mere temporary structures, used only by the males during the 

 spawning season ? If we admit the possibility of this condition 

 we can see how such structures might become permanent, be 

 produced in both sexes and subserve another function. 



FUNDULUS MAJALIS. 



(Killifish; Mayfish ; Rockfish.) 

 Sc.viial Dimorphism. 



The following passages, referring to sexual dimorphism, are 

 selected from Jordan and Evermann's account : 



"... anal fin very high in males, moderate in females ; ventrals long 

 in the males, reaching past front of anal ; . . . Males dark olivaceous 

 above ; sides silvery or somewhat golden, with about a dozen broad trans- 

 verse bars of the color of the back ; posterior part of the dorsal fin with a 

 black patch ; fins yellowish or pale. Females olivaceous above, white 

 below, a narrow black longitudinal stripe along sides about on the level of 

 the eye and as wide as the pupil ; below this two similar black stripes 

 anteriorly and one posteriorly, the upper one being interrupted ; one or 

 two black bars at the base of caudal. Females usually larger than the 

 males. A large male of this species, in high coloration, taken at Beaufort, 

 N. C., showed the following colors in life : Back olive, sides and belly 

 bright salmon yellow ; lower fins clear yellow ; pectorals and anals with 

 some dusky ; posterior edge of caudal dark ; dorsal nearly all black, a 

 large black ocellated spot on the last rays ; opercles and under parts of 

 head with an inky suffusion ; cheeks, top of head, and mouth bronze yel- 

 low ; sides with about eighteen narrow, dusky vertical bars." 



The "high coloration" referred to in the Beaufort male is 

 undoubtedly the "spawning plumage" and, although a some- 

 what more highly 'colored condition is described than I have 

 observed in any male at Woods Hole, the account is probably en- 

 tirely accurate for the species in more southern waters. The males 

 that I have observed (see Plate XXVII., 4) have the back and the 

 upper part of the sides almost black instead of olive as described ; 

 lower part of the sides and belly orange or golden yellow instead 

 of salmon yellow ; dorsal, anal and caudal fins golden with a 

 tendency toward dusky, the dorsal being only a trifle darker 

 than the other fins instead of being black as described above ; 



