Page:First course in biology (IA firstcourseinbio00bailrich).pdf/350

 vent. Are there more tail vertebræ or trunk vertebræ? Are there any neck (cervical) vertebræ (i.e. in front of those that bear ribs)? The first few ribs (how many?) are attached to the central body of the vertebræ. The remaining ribs are loosely attached to processes on the vertebræ. 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 homologous to true ribs; that is, true ribs in the higher vertebrates 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).