TRACES OF VOICES IN FISHES. 437 



geological time to see the numerous species of our birds 

 reduced to single representatives of each genus, and even 

 far fewer of so-called genera. With the avifauna thus 

 simplified, the differences that now exist between our 

 somber-hued songsters and the gayly-colored songless 

 birds were more distinctly drawn ; and this may have 

 been true also of our fishes. The vast influence brought 

 to bear upon all animals by their surroundings, and the 

 increasing struggle for existence, has evolved in later 

 times, and ever is evolving, innumerable variations in the 

 forms of life ; and these changes have in so great a meas- 

 ure obscured the conditions that once characterized both 

 our birds and fishes, in the matter of the relationship of 

 voice and color, that what I believe to have been once a 

 well-marked feature of animal life is now traced with 

 difficulty. Nevertheless, the many instances of apparent 

 voice that I have noticed, and their relationship to color, 

 induce me to believe that what is now scarcely a rule, 

 perhaps, among fishes, was once a law that governed 

 them. 



In studying these same fishes in another phase of their 

 habits, we see that, while all the species enumerated are 

 more or less active throughout the day, some of them 

 are far more so at night, and shun, if undisturbed, the 

 glare of the midday sunshine. These partially if not 

 strictly nocturnal species are those that I have considered 

 as having the power to give out or utter a truly vocal 

 sound, and they are the more plainly colored species. 

 The brilliant tints being of little or no use by night, ne- 

 cessitates the diurnal habits of those fishes possessing 

 them, while the nocturnal species, with a voice as a com- 

 pensation for the lack of color, are enabled to carry on a 

 courtship in part by its aid, which would be of little or 

 no use during the day. 



