158 UPLAND AND MEADOW. 



Relatively speaking, the fishes of the Delaware River 

 and its tributaries may be classified, iu regard to their 

 habits, as diurnal and nocturnal. It might almost be 

 said that there are no "fixed" habits. I have found 

 marked variations in every one of the most characteristic 

 habits of our birds ; and can see no reason why the same 

 degrees of variability should not likewise obtain among 

 mammals, reptiles, and fishes. In considering fishes as 

 either nocturnal or diurnal, I mean that they are so to 

 about the extent that owls are ; i. e., ranging from spe- 

 cies as diurnal as hawks to those that are nocturnal, or, 

 properly speaking, crepuscular. How often we hear the 

 phrase, " as blind as a bat " ! yet these mammals are not 

 averse to daylight, and only shun the glare of noonday. 

 In shady woods they are often found insect-hunting by 

 day ; and fly just as freely, and range abroad as generally, 

 on cloudy days, as during the gloaming throughout mid- 

 summer. 



Several years ago, when studying our fishes with ref- 

 erence to detecting supposed traces of voice possessed 

 by them, I concluded that the nocturnal, dull-colored 

 species had the power of uttering certain sounds, espe- 

 cially during the breeding-season ; while the diurnal 

 fislies were apparently voiceless, and were dependent 

 upon their gaudy coloration as a sexual attraction. 

 More recent observations have led me a step further, 

 and I am convinced that the colors of many species con- 

 tinue to play an important part in the struggle for ex- 

 istence throughout the interim from one breeding-season 

 to the next. It must be remembered that fishes, when 

 undisturbed by man's presence, are very different from 



