Pomona College, Claremont, California 85 



EXPLANATION OF FIGURES 



Figure 1. Stereographic reconstruction of the prostomium showing the position of the 

 brain inside of it and the position of the fiber tract inside of the brain. 

 The prostomium is shaded light, the brain darker and the fiber system 

 darkest. The prostomial sensory branches are not shown. X 50. 



Figure 2. Photograph of a wax reconstruction of the brain, showing the visceral and 

 nuchal ganglia darkened. The two hundred odd prostomial sensory 

 branches are shown in this reconstruction. X40. 



Figure 3. Diagram of the distribution of a segmental nerve. 



Figure 4. Stereographic reconstruction of the ventral side of the brain and of the 

 visceral nervous system. X40. 



Figure 5. Cross section through the front part of the prostomium cutting through 

 the front lobes of the brain. X50. 



Figure 6. Cross section of the main cross-connective part of the brain showing the 

 eye, the visceral ganglion and the canalicula that runs through this part 

 of the brain. X 50. 



Figure 7. Cross section of the brain in front of the main cross-connective part where 

 it has divided into two lateral halves. X50. 



Figure 8. Cross section through the ventral nerve cord near where the segmental 

 nerves come off showing giant cells. X 50. 



Figure 9. Cross section of the above between the origins of these nerves. X50. 



Figure 10. Enlarged view of the connection of one of the lobes of the fore brain 

 with the subcuticulum. XJ50. 



Figure 11. Giant cell and surrounding tissue. X250. 



Figure 12. Subcuticulum showing sense cells, mucous cells and regular subcuticular 

 cells. X500. 



Figure 13. Cross section of nuchal ganglia. X 50. 



Figure 14. Diagram of stereographic reconstruction, as described herein of two con- 

 centric cylinders; (a) is the first step, showing the cylinders with the 

 topographical reconstruction lines; (b) is the orientation guide, and (c) is 

 the shaded interpretation of (a). 



MEANING OF THE LETTERS 



(a) parapodia, (b) lateral brain lobes (c) frontal brain lobes, (d) brain cells, 

 (e) fiber tracts, (f) large brain cells, (g) giant cells in ventral cord, (h) mucous 

 gland cells, (i) nuchal ganglia, (j) suboesophageal ganglion, (k) pedicle of neuro- 

 cord, (1) muscle tissue, (m) outer or maxillary nervous system, (n) inner or super- 

 pharyngeal nervous system, (o) maxillary slit opening into denticular pouch, (p) gang- 

 lia forming clrcumintestinal ring, (q) cavity which separates the dorsal from the 

 ventral parts of the brain, (r) labial nerves, (s) subcuticular cell, (t) mucous gland 

 cell, (u) sense cell, (v) visceral ganglion, (w) neural canal. 



