SPAWNING BEHAVIOR IN FUNDULUS HETEROCLITUS. 325 



The enormous difference in the fin coloration of the two sexes 

 should also be emphasized, those of the female being almost de- 

 void of pigment while those of the male, although more deeply 

 colored in the spawning season, are always markedly pigmented, 

 the pigment being laid down is such a way as to produce a mot- 

 tled pattern. The posterior and proximal half of the dorsal is, 

 however, always much darker than any other area on the fins and 

 is the equivalent of the much more distinct spot seen on the dor- 

 sal of male Fundiilus inajalis. There is also a marked difference 

 in the shape and in the strength or stiffness of these fins in the 

 two sexes. In the male there is a pronounced posterior prolonga- 

 tion of both fins, especially the anal. These fins are stronger and 

 better provided with muscle in the male than in the female and 

 hence are better fitted for clasping organs. 



DISCUSSION OF THE SEASONAL CHANGES. 



The seasonal changes may be classified as follows : 

 In the female : 



1. Paling of the general body coloration. 



2. Distension of the abdomen with eggs and consequent less- 

 ened activity. 



3. Thickening and inflammation of the anal fin. 

 In the male : 



1. Intensification of pigmentation in definite regions. 



2. Acquisition of a steely blue gleam in the scales of certain 

 regions, (i and 2 are spoken of collectively as "spawning 

 plumage.") 



3. Development of certain temporary organs on the scales that 

 I have chosen to call " contact organs." 



i. The paling of the general body coloration in the female and 

 the intensification of pigmentation in the male might be attributed 

 to the opposite metabolic conditions prevailing in the two sexes 

 at this period. The female, having to sacrifice so much of her 

 vitality for egg production, must have a lowered somatic metabo- 

 lism, the index of which is the diminished production of pigment. 

 The male, on the other hand, seems to have much excess vitality, 

 since the production of sperm is far less taxing on somatic vitality 

 than is the production of eggs. The deposition of pigment here 



