114 



BEGINNERS' ZOOLOGY 



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- 



FlG. 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 fiti 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 

 Fig. 214. — Soft-rayed and Spiny-rayed Fins. _ ..,.,,„., 



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). 



