Lewis. — Nervous Syst, Polychaeta. 



PLATE 2. 



Figs. 6, 7. Diagrams of the nerve cord in the ninth and tenth segments respect- 

 ively, to show the distribution of the giant ganglion cells and their 

 relation to Leydig's fibre. The two horizontal lines mark the posi- 

 tion of the setEe. The two figures are to be imagined as united at j3. 



Figs. 8, 9. Sections of different giant ganglion cells from the region of the sub- 

 cesophageal ganglion, showing in each cell two spheres, each with 

 centrosome and radiations. Tiie nucleus was not cut in either case. 



Fig. 10. Section of giant ganglion cell, showing an outpocketing of the cell in 

 which the nucleus lies. 



Figs. 11, 12. Sections of different ganglion cells, showing centrosome and radiations. 



Figs. 13, 14. Two successive sections of the same cell, showing nucleus and two 

 centrospheres. 

 N. B. By an error in transferring, Figure 14 is upside down. 



Fig. 15. Cross section of Leydig's fibre. X 1000. 



Fig. 16. Longitudinal section of Leydig's fibre. X 1000, 



