TRACES OF VOICES IN FISHES. 439 



of silvery bubbles that escape from the mouth of the 

 mud sunfish when, shall I say, calling to its mate. At 

 night, I believe, the sunfish rests from his labors. I 

 have not been able to detect any of his spring-time vivaci- 

 ty after sunset, and hence I am led 'to conclude that his 

 sole dependence in securing a mate is in his brilliant 

 coloring. 



What a contrast is presented in the lazy, dull-colored 

 cat-fish that slowly wanders over the muddy bed of the 

 stream ; if perchance he is moving about at all during the 

 day ! Not a motion can be detected that is not referable, 

 without doubt, to so prosaic a matter as the search for 

 food. If a dozen or more come together, it is but to 

 hunt in concert, and nothing of the nature of a contest is 

 to be seen. But after sunset every one of them becomes 

 suddenly more animated, and there is a marked restless- 

 ness in every movement, as they congregate in large num- 

 bers in some limited area. At such a time, their presence 

 is to be detected not only by the aid of submarine lan- 

 terns, and all the troublesome helps that one must employ 

 to study fishes at night, but there is an opportunity given 

 to use the ears as well as eyes, and by careful, patient 

 watching and waiting we may hear, even from the deeper 

 waters, a gentle humming sound which, if noticed at all, 

 would by most people be referred to the insect-life teem- 

 ing about them. If, knowing or suspecting the true origin 

 of this gentle murmur, we can, without alarming the fish, 

 float our boat directly above them, we will find that scores 

 of chains of little air-bubbles are rising to the surface ; and 

 as the sound increases or dies away, in proportion to the 

 abundance or absence of the bubbles, it is safe to refer it 

 to the fishes, which produce it by voluntarily expelling 

 the air from their bodies. 



I have not the space here to enumerate all the cir- 



