88 



ZOOLOGY. 



mented. In the higher Vertebrates it is not manifest externally, but is 

 shown in the vertebrae, the nerves, etc. 



119. Appendages. Nearly all the animals, whatever the fundamental 

 symmetry may be, have appendages of one kind or another for locomo- 

 tion, capture of food, protection, respiration, and the like. These out- 

 growths from the body may be generally distributed over the body surface 

 (as cilia in some Protozoa and free-swimming larvae) ; or radially ar- 

 ranged, often about the mouth, as in many radially symmetrical animals 

 (Figs. 47, 48, 79) ; or in a right and left series in bilaterally sym- 



FIG. 49. 



FIG. 49. Diagram of the cross section of a fish, showing the bilateral symmetry of 

 the parts: dv, dorsoventral axis; rl, right-left axis, a.p., anterior appendage; b.c., body 

 cavity; ch, notochord; d.f., dorsal fin; g, gut; h, heart; h.a., haemal arch; m, muscles; 

 n.a., neural arch; sp, spinal cord; v.c., vertebral column. 



Questions on the figure. In what respects is the symmetry as shown 

 in this cross-section different from that shown in the cross-section of sea- 

 anemone? Compare carefully, and express your conclusions in terms of 

 the axes and their poles. Find other figures in this book illustrating 

 bilateral symmetry. 



