242 GENERAL ZOOLOGY 



Perch take no care of their eggs, and may even devour 

 them or their young. Other species of fishes often follow 

 perch during the spawning season to feed upon the egg 

 strings. The young are very sluggish until the yolk sac has 

 been absorbed, then quickly learn to shift for themselves. 



GENERAL REMARKS ON FISHES 



The thirteen thousand species of fishes now in existence 

 show a wide range of variation in structure and habits. 



The morays and eels have long snake-like bodies; the 

 puffers and globefishes are more or less spherical in form; 

 the goose-fishes have very large heads, the sunfishes have 

 large bodies and very small heads; most fishes are well 

 covered with scales, but the catfish es have none. The fins 

 vary greatly in size, structure and position. There is end- 

 less variation, yet all fishes are recognizable as such, for they 

 breathe through gills and are without fingers or toes on 

 their paired limbs. 



The feeding habits of fishes are often very interesting and 

 peculiar. The herring eats diatoms and other microscopic 

 organisms which it strains from the ocean. One scientist 

 has said that he could predict the herring catch by the 

 number of sunshiny days so directly is the growth of 

 diatoms dependent upon light from the sun, and so im- 

 t portant are these minute plants as food for the herring. The 

 black swallower takes whole fish into its stomach which 

 greatly exceed its own size. Various fishes feed exclusively 

 on plants, or fish, or other particular foods. Some are thus 

 greatly specialized, others will eat practically anything 

 they encounter. 



The only method of locomotion in most fishes is swimming 

 by using the fins, but there are many exceptions. The 

 beach skippers along the shores of some tropical seas seldom 

 enter the water but hop about by using the pectoral fins and 

 tail. The climbing-perch^ is not only able to come on land, 

 but is said to climb trees and catch insects. Flying fishes 



