182 



THE TROUT 



intermediate tadpole stage, in which they are known 

 as f alevins.' Attached to them underneath is a kind 

 of bladder nearly as large as their bodies, known as 

 the umbilical vesicle or yolk sac. 



The American fish-culturist, Seth Green, has aptly 

 described it as ' Nature's feeding-bottle.' It contains 

 nourishment in the shape of oil globules, which are alone 

 sufficient to support the infant until it is able to eat. 



The accompanying graphic diagrams (fig. 12), taken 



D, 



FIG. 12. 



No. i. 



THE LEFT SIDE OF THE FISH. 



A The heart. 



B JY1 ain trunk artery. 



C Large vein. 



D Oil globules, only two of which 

 are introduced for sake of dis- 

 tinctness. 



No. 2. 



THE RIGHT SIDE OF THE FISH. 



a The heart. 

 b Main trunk artery. 

 c The liver. 

 d Oil globules. 



Large vein from liver to heart. 

 / Branch from main artery to liver. 



