146 VERTEBRATE ZOOLOGY 



voracious and omnivorous of fishes. It breeds far out at sea, and 

 its tiny pelagic eggs are almost inconceivably numerous; as many as 

 nine million eggs have been estimated as being laid by a single large 



y 



FIG. 85. Gadus mmrhua (Cod), an, anus; cf, caudal fin; dfl-3, dorsal fins; 

 mx, maxilla; pct.f, pectoral fin; pmx, premaxilla; pv.f, pelvic fin; vf. 1 and 2, 

 ventral fins. (From Parker and Haswell, after Cuvier.) 



female in one season. Most of us who have been children need 

 hardly be reminded of the somewhat unpleasant fact that the 

 liver of the Cod is the source of a highly nutritious and readily 

 digested oil. Relatives of the Cod are the Haddock, the Pollock, 

 the Burbot, the Hake, and some aberrant and degenerate deep- 

 sea forms. 



The Spiny-Rayed Fishes (Acanthopterygii) . This tremendous 

 assemblage of modernized fishes reminds one of the passerine 

 birds, because they are the most modern of the sub-orders and 

 show a more extensive adaptive radiation than do any of the 

 other groups. The Acanthopterygii comprise no less than thirty- 

 six families including such familiar forms as the Bass, Perch, Flounder, 

 Goby, etc., and a host of less familiar types. 



The common Perch is as good a type to illustrate the sub-order as 

 any, though it is perhaps the most generalized member of the group. 

 Many of the others tend to become high, compressed, and short- 

 bodied, such as the little fresh-water sun-fish. Other forms that live 

 in the open seas have carried out this line of development till the 

 dorso-ventral axis appears to overshadow the primary and the bi- 

 lateral axes, as is the case in some of the Acanthiuridce, a family 

 which is strikingly exemplified by Zanclus (Fig. 86) . It is from such 

 types as this that the members of the curious sub-order Pledognaihi 

 are thought to have been derived 



