318 GENERAL ZOOLOGY 



as early as March ; in New England, in May. The eggs are 

 laid in shallow water in a ribbon-like mass (Fig. 161), which, 

 after absorption of water, is sometimes six or seven feet 

 long and two inches in diameter. This great mass, which 

 contains thousands of eggs (over a hundred thousand have 

 been counted in a two-pound perch), is fertilized by the 

 male emitting his sperm (milt) over it. The eggs form a 

 large part of the food of other fishes and aquatic birds. 

 In from two to four weeks, depending on the temperature, 



the young perch hatches 



from the egg, at first with 



the yolk sac attached to 



the ventral surface (compare 



Fig. 162). After absorption 



Fig. 162. Young sturgeon with of the yolk sac, which soon 



yolk sac. (Enlarged) occurs, the young perch dif- 



After Ryder f ers f rom the adult chiefly in 



its smaller size and lighter 

 color, and in the relatively greater size of head and eyes as 

 compared with the rest of the body. 



Relation to Environment. The whole organization of the 

 perch marks it at once as one of the predatory type of ani- 

 mals, — those which hunt their food and depend upon their 

 superior strength or agility to obtain it. As Izaak Walton 

 long ago said of its European relative, the yellow perch is 

 'one of the fishes of prey that, like the Pike and Trout, 

 carries his teeth in his mouth, not in his throat, and dare 

 venture to kill and devour another fish." The shape of the 

 body is precisely that which offers least resistance to mo- 

 tion in the water. The strong lateral muscles give great 

 power to the caudal fin, which, by a slight lateral motion, 

 drives the fish forcibly forward. Lateral and median fins 

 assist in maintaining equilibrium, in steering, and in raising 

 and lowering the fish in the water. 



