22 THE PRACTICAL FISHERMAN. 



above table in his memory first, that it belongs to the true fish as- 

 distinct from cartilaginous (for no cartilaginous fish can have spines) ; 

 second, that it belongs to first order of spiny finned fishes or 

 A-canthopterigiana ; and, thirdly, if it has spines on the back, it is of 

 the percidae family. Herein lies one of the practical uses of 

 ichthyology. The determination of the different genera in the same 

 genus of fishes requires more minute and careful comparison than a 

 decision of the order. The tyro, for example, would probably find it 

 difficult to instantly distinguish between the dace and chub, and, indeed, 

 when both are young, the difference is infinitesimal. As I intend to 

 revert to each fish in the order above given, I shall reserve any further 

 remarks on the distinctive characteristics of each until that time. 



It may now be well to consider in a succinct manner the various 

 principal qualities and attributes which fish have in common. First, then, 

 if we disregard the idea which has obtained in reference to eels being 

 viviparous, or bringing forth their young alive, it may be stated 

 that, in scientific phraseology, all fish are oviparous vertebrata, or 

 creatures with articulated backbones bringing forth eggs. They have 

 a double circulation, and breathe through the medium of water. Like 

 other animals of the same class, they have a spinal column formed of 

 four parallel sections, two of which receive nerves of sensation 

 from the surface of the body, and the other receive the nerves of 

 volition or action. The spinal cord enlarges at one end of this column 

 and forms the brain, which in the pike is in weight as 1 in 3000 in 

 proportion to the body, and in carp (the subtlest of the soft-fmned fish) 

 as 1 in 500. 



The Branchia or gills, or breathing apparatus, are, as need scarcely 

 be stated, compactly arranged in the opercula or gill covers of the 

 creature, and consists of four or five cartilaginous fringed arches. Under 

 the microscope the se present a very beautiful appearance, as they continue 

 their work, receiving the water, separating the air from it, and passing 

 it on through the anterior opening, together with whatever of carbon is 

 given off. And here it is worthy of remark that the water is not 

 decomposed, but the oxygen is only mechanically separated from the 

 water. A fish cannot live in a tumbler of water placed in the receiver of 

 an air pump. Some fish will, however, continue to live out of water a 

 considerable time. In the ordinary way the gill filaments get stuck 

 together as they dry, and the fish then becomes asphyxiated and dies. 



The fins of a fish serve variously in the different families and species. 

 Generally speaking the foEowing description of their functions is a 

 correct one. I extract it from " Paley's Natural Theology," (the author 

 of which probably got it chiefly from Goldsmith's "History of Animated 



