IS 



Joiirniil of Entiinv>l(i^:y and Znoloj:) 



process passing to the periphery, the other running centrally. The 

 number, position, size and form of the cells is symmetrical in both 

 halves of the ganglion, also the processes are symmetrically dis- 

 posed. Commissural fibers bind right and left halves of the 

 ganglion. Some fibers leave the brain directly from ganglion cells 

 while others enter or leave by way of paired nerve fibers which 

 connect directly with the central fibrous core of the ganglion. 



The ganglion cells are said to be al)solutely constant as to their 

 position, form and relative size. The position of the nuclei in the 

 cytoplasm is not so constant. The larger and smaller fibers seem 

 also constant in number and position. 



Sense cells are found at the surface of the body more or less 

 removed from the surface. Single sensory nerve cells with two 

 nuclei end directly in the surface. Another kind of sensory ending 



A. Rhizotidd, front and profile, showinj; position of the nervous system. 

 Zelinka. 



B. Embryonic stage of a rotifer showing position of nervous system in 

 two dark masses. Zelinka. 



C. Fnillaria, showing position of nerve strands in the body. 



D. Position of nervous system in rotifer after Pelage et Herouard. 



E. Nervous system of Floscularia after Hudson and Gosse. 



F. DincopiiH, showing nervous system, after Zelinka. 



G. Sense organs with nerves from the brain shown in cross section 

 after D. & H. 



H. Nervous system of Echinoderes from several sources. 



I. Nervous system of Echinoderes from above. Schepotieff, but much 

 changed. 



J. K. Head end of Chaeltnintun from helow J. and above K. showing brain 

 and sense hairs. Zelinka. 



