1 88 Journal of Comparative Neurology. 



from the half grown individual lo cm. long, to the full grown 

 fish of 20 cm. there is a difference in the size of the cells keep- 

 ing pace with the growth of the body. In the adult there is 

 considerable variation in the size of the cells. The smaller hav- 

 ing a minimum diameter of 40 jn , the larger of 70 /z , with an 

 extreme length to the beginning of the axis cylinder of i$o jn . 

 The number of cells in a single fish is between 35 and 40, and 

 seems to be fairly constant regardless to the age or size of the 

 fish. 



Fzg. 4. Five Giant Ganglion Cells showing variation in form and branch- 

 ing oi the neurites. 



The form of these giant cells, though always characteristic, 

 is very variable. In young specimens of Ctenolabrus 3 cm. in 

 length the cells show much greater regularity in form and dis- 

 tribution than in the adult. In the anterior part of the cord 

 they lie closely together, the intervals increasing regularly pos- 

 teriorly. The cells are usually rounded, but anteriorly mutual 

 pressure may give them a somewhat angular outline. Oc- 

 casionally in the smallest specimens examined, the cells are 

 uniformly dorso-ventrally flattened, approaching a discoid or 

 lenticular form. 



In the adult the simplest form is approximately spherical 

 (Fig. 5), but this form grades off to the pyriform which is the 

 most typical (Fig. i c, Fig. 4 b). The tapering end is ventral 

 and from it comes off the axis-cylinder. This may pass off 



