18 Journal of Entomology and Zoology 
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 absolutely 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. Rhizotida, front and profile, showing position of the nervous system. 
Zelinka. 
B. Embryonic stage of a rotifer showing position of nervous system in 
two dark masses. Zelinka. 
Frullaria, showing position of nerve strands in the body. 
Position of nervous system in rotifer after Delage et Herouard. 
Nervous system of Floscularia after Hudson and Gosse. 
Discopus, showing nervous system, after Zelinka. 
. Sense organs with nerves from the brain shown in cross section 
after D. & H. 
H. Nervous system of Hchinoderes from several sources. 
I. Nervous system of EHchinoderes from above. Schepotieff, but much 
changed. : 
J. K. Head end of Chaetonotus from below J. and aboye K. showing brain 
and sense hairs. Zelinka. 
Ano O 
