142 Embryology and Growth of Fishes 



in the young, the fins are lower, the appendages less developed, 

 and the body more slender in the young than in the adult. But 



to most of these distinctions 

 there are numerous exceptions, 

 and in some fish there is a 

 change so marked as to be 

 fairly called a metamorphosis. 

 In such cases the young fish in 

 its first condition is properly 

 called a larva. The larva of 

 the lamprey {Peiromyzou) is 

 nearly blind and toothless, with 

 slender head, and was long sup- 

 posed to belong to a different 

 genus {Ainnioca^tes) from the 

 adult. The larva of sharks and rays, and also of Dipnoans 

 and Crossopterygians, are provided with bushy external gills, 



Fig. 106.— Larva (called Tholichthys) 

 of Chtrtodon sedentariiis (Poey). 

 Cuba. (After Liitken,) 



Fig. 107. — Butterfly-fish, Chcvtodon capistratus Linnaeus. Jamaica. 



which disappear in the process of development. In most 

 soft-rayed fishes the embryonic fringe which precedes the 



