The adult organisation of Paragordius varius. 405 
ones similar to those on the lateral aspect, and much larger giant 
cells (Fig. 24, Pl. 38; Figs. 26, 31, Pl. 39). These giant cells are 
much less numerous than the others: in 406 sections from different 
regions of the body, from 39 to 53 of these cells were found; that 
is, certainly 39 were present, while the remainder may not have been 
sectioned so as to show their full diameters, or might have been inter- 
mediate in size between the giant cells and the small cells. Four or 
five was the greatest number found in any twenty consecutive sections. 
Sometimes a paired arrangement of these cells occurs, but they 
generally are not paired and are placed irregularly one behind 
the other (some in the median line, some to the right or left of this 
line). 
As far as can be determined from an examination of them as 
seen on sections, these giant cells appear to be bipolar with two large 
processes proceeding from that surface of the cell directed towards 
the fibrous core of the nerve cord; this is to be clearly seen on two 
cells of the Figs. 24, 26; in the cases where only one process is seen 
it is then probable that the other process lies out of the plane of the 
section. Many of the smaller type of chromophobic nerve cells appear 
to be bipolar or even multipolar (Figs. 29, 30, Pl. 39), but it is 
difficult to determine their exact form since all fixatives cause more 
less shrinkage in these cells, so that their outlines appear generally 
irregular. All these cells are membraneless. 
The processes of these cells constitute the chromophobic nerve fibres 
of the nerve cord; in the Figs. 22, 24, 25, Pl. 38; Fig. 26, Pl. 39 these are 
shown of a lighter color than those of the chromophilic nerve cells. These 
chromophobic fibres can only be clearly seen on the thinnest sections 
when deeply stained with iron-haematoxylin. Within the nerve cord 
I have not been able to follow the course of a single fibre for more 
than a very short distance, and so could not determine whether they 
ramify. On cross section they appear larger than the chromophilic 
fibres as a rule, and several often appear to fuse together (which is 
probably due to the action of the fixatives). 
These chromophobic nerve elements probably are motor and 
visceral in their function, as will be shown in the description of the 
peripheral nervous system. 
The chromophilic elements. These are characterized by 
their deep-staining quality, and with the usual methods of staining 
are the only elements to be seen clearly (the sharply pronounced ele- 
ments of Figs. 22, 24, 25, Pl. 38; Fig. 26, Pl. 39). The nucleus 
