PISCES 139 



in the same parent stream. This does not necessarily imply any 

 marvelous homing instinct or geographic sense, for it has been found 

 that when the Salmon goes to sea it does not wander very far from the 

 mouth of the particular river down which it has come. The instinct 

 to spawn in the smaller streams must, nevertheless, be extremely 

 impelling, for they frequently wear themselves out and die owing to 

 the arduous up-stream journey of often more than a thousand miles, 

 through rapids and even over water-falls of considerable height. It 



o 



FIG. 76. Salmon, Salmo fario. a. I, adipose lobe of pelvic fin; an, anus; c.f, 

 caudal fin; d.f. 1, first dorsal fin; d.f. 2, second dorsal or adipose fin; 1. 1, lateral 

 line; op, operculum; pct.f, pectoral fin; pv.f, pelvic fin; v.f. ventral fin. (From 

 Parker and Haswell, after Jardine.) 



is said that few, if any, survive to go down-stream and out to sea 

 again; a statement that seems to be out of accord with the fact that 

 some very large specimens, evidently much over five years old, are 

 captured in every salmon river. 



The great Herring family (Clupeidce) consists of fishes of de - 

 cidedly generalized proportions and characters. They are diagram- 

 matic teleosts. Fossil Herrings practically like those of the present 

 have been found well preserved in Cretaceous rocks. The family 

 includes also Shad, Anchovies, and White-fishes, which are among the 

 most important of the world's food fishes. 



By no means all of the Malacopterygii are generalized types, for 

 there has been a very considerable adaptive radiation within the 

 group. Among the specialized and senescent types are: the mormy- 

 rids of the Nile, remarkable electric fishes that were pictured by the 

 early Egyptians; eel-like types such as Gymnarchus; proboscis- 

 fishes such as Gnaihonemus; and several deep-sea forms with degen- 

 erate and otherwise aberrant characters. 



