36 Journal of Entomology and Zoology 
cells in zones. There is usually a central more or less clear zone, next on each side 
a rather dense cell area and next on each side a very dense cell area, then a narrow 
nearly clear zone on each side again. 
As a rule slightly larger cells are found near the nerve trunks and as some of 
these seem to send long branches out into the lateral trunks, they may be motor or 
sensory, the association neurones are probably the smaller cells in farther. The cells 
seem multipolar in most cases and in fact much more modified than the cells of starfish 
or sea-urchin. Figs. 9 and 10. 
REFERENCES 
Delage and Herouard 1903 
Traite de zoologie concrete. T. iii. Les Echinoderms. ~ 
Hamann, O. 1887 
Beitrage zur Histologie der Echinodermen. Jenna Zeit. Nat. W. xxi. 
Hilton, W. A. 1917 
Some remarks on the nervous system of two sea-urchins. Jour. ent. and zoo. vol. 
ix, no. 4. 
(Contribution from the Zoological Laboratory of Pomona College) 
g y 9) L 
Explanation of Figures 
Fig. 1. Diagram of one fifth of Aristotle’s lantern of Dendraster showing three 
loops of the circumoral nerve ring, and parts of three radial nerves, the central one 
partly hidden at its origin by the lantern. The nerves are in black. X9. 
Fig. 2. Drawing of part of the first part of an oral radial nerve. X9. 
Fig. 3. Drawing of the lower end of an oral radial nerve. X9. 
Fig. 4.- Drawing of the upper part of an aboral radial nerve. The eye spot 
region is up in the figure. X9. 
Fig. 5. Camera lucida drawing of a part of an aboral nerve showing position of 
cell areas. X70. 
Fig. 6. Drawing of a section of an oral radial nerve. X300. 
Fig. 7. Drawing of a section of circumoral nerve. X300. 
Fig. 8. Drawing of a section of aboral nerve. X300. 
Fig. 9. Nerve cells from central regions of a radial nerve. The arrangement 
is as shown in the drawing, cells of various levels shown as one layer. Some of the 
processes possibly relate nearby cells, but most fibers run into the general fibrous mass. 
All fibers or fibrils are small. There is some indication of tigroid substance in some 
of the cells. X450. 
Fig. 10. Nerve cells from near a lateral branch from the radial band. X450. 
