ZOOLOGY 



FIG. 37. 



FIG. 37. Diagram shoving arrangement of the nervous matter in Starfish, c, ganglionated ring 



about the mouth; o, mouth; r.n., radial nerve in each arm. 



FlG. 38. The nervous system of the Clam, from the dorsal aspect, c, anterior; o, mouth; e.g., 

 cerebral ganglia (brain); p.g., pedal ganglia; v.g., visceral ganglia. 



Questions on Fig. 37. Describe in your own terms the way in which the 

 principal nerve elements are arranged in the starfish? Compare it with those 

 which follow. In what respects similar? In what unlike them? 



FIG. 39. 



FIG. 40. 

 CL 



FIG. 39. Arrangement of the nervous material in the anterior end of an Oligochete Worm, 

 seen in profile. That part of the body wall nearest the observer is supposed to be removed, a, 

 anterior; b.w., body wall; g, dorsal ganglia (brain); g', ventral chain of ganglia; n, nerve ring around 

 the pharynx; o, mouth; p, pharynx. 



FIG. 40. The central nervous system in a Leech. Lettering as in Fig. 39. 



Questions on figures 38, 39, and 40. How is the nervous matter related to the 

 digestive tract and to the animal as a whole in all of these figures ? Compare with 

 figures in other texts. Is there any apparent correlation between the form, 

 symmetry or segmentation of the animal and the arrangement of the nervous 

 material? Can you state your conclusion as a law? 



