2 
The dendrites are small and difficult to see in the stained prepar- 
ations used; their presence does not sensibly disturb the spherical 
contour of the cells. 
The neurites are ventral prolongations of the cell body and pass 
directly down into the cord. They may incline either cephalad or 
caudad upon leaving the cell, but when they have passed about one- 
half of the distance to the central canal each one leaves the median 
line, and, bending or curving towards the tail, enters either the right 
or left one of two symmetrical fibre bundles which lie mesad to the 
dorsal horns of the gray matter, and above, and parallel to, the central 
canal. This course of the neurites was observed and confirmed by the 
following methods. In longitudinal, vertical sections of the cord the 
neurite was traced from the 
cellto the fibre bundle and 
followed for some distance 
towards the tail in this 
bundle. This was done with 
exactness in over 150 cells 
taken from nine different 
fishes (see Fig. 1). 
Fig, 1. Longitudinal, vertical 
section of cord of Paralichthys d. 
giant cell (c) whose neurite (a) is 
seen entering the fibre-bundle (4). 
Again, in the case of one fish, longitudinal vertical sections were 
made of each segment and the cells in each were counted. Also a 
few transverse sections were taken from the posterior end of each 
segment before making the longitudinal sections, and the fibres of the 
two fibre bundles I have mentioned were counted. The number of 
fibres in each transverse section agreed very closely with the number 
of the cells in all the segments preceding it. The following is a table 
of these results: 
No. of segment Cells in segment Fibres in transverse sec- 
tion of posterior end 
1—3 78 73 
4—5 75 149 
6—7 63 211 
Beyond this point (7th spinal segment) the cells and fibres extended, 
of course, but the counting of fibres was invalidated by the approxim- 
ation of fibres coming from internal cells of another character. This 
fact also prevented, for the time, any accurate observations on the fur- 
