114 



ANIMAL BIOLOGY 



vent. Are there more tail vertebrae or trunk vertebrae ? 

 Are there any neck (cervical) vertebrae (i.e. in front of 

 those that bear ribs)? The first few ribs (how many ?) are 

 attached to the central body of the vertebrae. The re- 



FIG. 213. 



maining ribs are loosely attached to processes on the 

 vertebrae. The ribs of bony fishes are not homologous 

 with the ribs of the higher vertebrates. In most fishes 

 there are bones called intermuscular bones attached to the 

 first ribs (how many in the perch ?) which are possibly homol- 

 ogous to true ribs ; that is, true ribs in the higher verte- 

 brates may have been developed from such beginnings. 



Which, if any, of the fin skeletons (Fig. 214) are not 

 attached to the general skeleton ? Which fin is composed 

 chiefly of tapering, pointed rays ? Which fins consist of 



rays which sub- 

 divide and widen 

 toward the end ? 

 Which kind are 

 stiff, and which are 

 flexible? Which of 

 the fin rays are segmented, or in two portions ? The outer 

 segment is called the radial, the inner the basal segment. 

 Which segments are longer ? There is one basal segment 

 that lacks a radial segment; find it (Fig. 212). 



FIG. 214. SOFT-RAYED AND SPINY-RAYED FINS. 



