Pomona College, Claremont, California 



13 



4. Dorsal collar nerve somewhat cut off from the two follow- 



ing. 



5. Dorsal proboscis nerve continued above. 



6. Central nervous system running through the central region 

 of the collar on the dorsal side and continuous above with the pro- 

 boscis nerves and below the collar with the dorsal body nerve. 



The dorsal nerve of the collar and the thick central nervous 

 system of the collar are more or less joined by the strands and 

 they together make a sort of nerve tube thin on the dorsal side but 

 thick below. 



The histological structure of the nervous system reveals be- 

 sides the usual epithelial cells of the surface, bipolar supportive 





Fig. 24. Nervous System and Sense Organs of Enteropneusta. A. Diagram 

 of Balanoglossiis showing position of the nervous system. B. Anoth- 

 er diagram of Balanoglossiis in sectional view. Spengel. C, D. 

 Sections of developing nervous system. Morgan. E. Larva after 

 Herder. F. Apical eye of tornaria larva. Spengel. G. Eyes of 

 Tornaria after Morgan. H. Eye of Tornaria after Spengel. 



