34 



THE AQL^ARIUM, APRIL, 1893. 



intelligible, especially so where encum- 

 bered with technical terms and phrases 

 that serve to befog the mere observer 

 and discourage his efforts to learn. 



We will then begin our study of fishes 

 as we see them swimming in the water. 



Upon approaching an aquarium or 

 pond in which there are fish, we see 

 something moving about in the water 

 with more or less grace, and which to 

 the eye is beautiful, pleasing, and inter- 

 esting. To say that they are fish is 

 very true, but the name does not neces- 

 sarily convey any precise idea of the 

 form or shape of the moving animal. 



80 great, indeed, is the diversity of 

 forms that exist, that it is impossible to 

 establish any standard by which the idea 

 of outward appearance may be ade- 

 quately conveyed to the mind ; for in- 

 stance, the flounder, the torpedo, the 

 pumpkin-seed, sun, and the eel are all 

 fish in the full acceptation of the term, 

 yet neither of them resemble the carp, 

 the trout, or the common gold-fish, 

 with which almost everybody is more 

 or less familiar. 



There are two dominant characteris- 

 tics, however, which pertain to fish, 

 and by which they are known to nearly 

 everyone. First : in nearly all cases 

 the body is covered with scales ; and 

 second : the limbs are always rejore- 

 sented by organs denominated fins, no 

 matter how rudimentary or perfect 

 their development may be. 



We will consider, first, the scales, as 

 they are, by the peculiar appearance 

 they give to the fish, almost the first 

 thing to strike the eye. 



These scales, as they are called, are 

 so arranged upon the surface of the 

 body that they overlap one another, 

 just in the manner a carpenter lays 

 shingles on a roof, being disposed in 

 such a way that the friction incident 



\\]iO\\ the movements of the fish in the 

 water is reduced to the smallest propor- 

 tion. As the fish grows older and 

 larger the scales increase in size, being 

 variously proportioned in different 

 species. 



Near the middle of the body and run- 

 ning along each side of the fish, there 

 is a line or band of scales that possess 

 peculiarities distinguishing them from 

 other scales. These scales, in one en- 

 tire row. are pierced with a tubular 

 aperture, and the tube of which they 

 are the exit are quite distinct and form 

 the " lateral line," as the band is usually 

 called Through these tubes a shiny 

 substance or mucous is exuded, which 

 covers the entire body, seemingly for 

 the purpose of making the fish water- 

 proof and of further reducing the fric-. 

 tion in the water. 



Scale from lateral line of Goldfish. CEiilarged). 



The tubes always point from the 

 matrix or root of the scale toward the 

 tail of the fish, discharging their 

 mucous in that direction. It is scales 

 of this description that naturalists refer 

 to when seeking to learn the species to 

 which the fish belongs, because the 

 peculiarities of their structure and 

 function make them conspicuous 

 amongst the rest. 



Scales of either kind are readily re- 

 placed by nature when, from accident 

 or otherwise, they happen to be re- 

 moved. The color of the scales differ 



