342 H. H. NEWMAN. 



9. The generally aggressive and warlike aspect of the male is 

 in striking contrast to the comparatively mild and timid aspect of 

 the female. This contrast is more striking in Cyprinodon than 

 in the species of Fnndnhis examined. 



10. This exceedingly fierce aspect of the male is largely due 

 to the very marked height of the dorsal fin and his method of 

 carrying it spread to the utmost. 



SUMMARY AND CONCLUSIONS. 



Classification of Secondary Sexual Characters. 



I. Of the permanent differences the following is a list : 



1. Relative size of the sexes. 



2. General body form. 



3. Relative sizes of the various fins. 



4. Shape of the various fins. 



5. Color pattern (a) on the body, (/?) on the fins. 



6. Quality and intensity of coloration, whether it consists of 

 pigmentation or of iridescence. 



7. Relative abundance of the sexes. 



11. Of the temporary differences that appear only during the 

 spawning season the following is a list : 



1. The distended abdomen of the female. 



2. The swollen and inflamed anal fin in the females of Fundulus 



3. The marked intensification of coloration and iridescence in 

 the males, both on the body and on certain fins. 



4. The paling of color in the females. 



5. Contact organs in spawning males. 



6. The increased activity of the males, accompanied by an in- 



crease in courage. 



7. The coyness of the females, especially in Cyprinodon. 



All of these secondary sexual characters can, I believe, be 

 shown to be either direct adaptations to the sexual life of the fish 

 or necessary accompaniments of the high physiological tone that 

 accompanies the sexual climax. 



Of the permanent characters the most obviously adaptive are 

 those that have to do with the differences in size of certain fins in 

 the two sexes. Without reasonable doubt the enlarged dorsal, 

 anal and ventrals are adaptations to facilitate clasping. The ori- 



