118 Wiıuvıam A. Hıuron, 
Distaplia, Amaroecium, Ascidia and Phallusia, respectively. I did not 
find this projection in all the specimens, nor did I find nerve cells 
in it. Possibly it represents a part of the rapheal nerve cord. 
The structure of the ganglion. 
The nerve cells are arranged chiefly about the periphery of the 
œanglion, in cross sections of which they appear as a deeply staining 
border around the central fibrous core (Figs. D, E). The thickness 
of this peripheral mass of cells varies considerably in different 
regions. At various places, where the nerve trunks come off, especi- 
ally in the region of the larger trunks, the cells of the border be- 
come much reduced in number or disappear in large part as the fibers 
sweep into or from the more central portion of the ganglion (Figs. E, F). 
Some of the cells are large, others are small, many of the larger 
ones being located at the outer surface of the ganglion. 
Blood is abundant in the gland and is present to some degree 
also in the peripheral layer of cells in the ganglion. 
The central, more fibrous mass of the ganglion is not without 
cells, but they are widely scattered. Many of these are very small 
and apparently are not functional nerve cells The central area 
contains cells which not only as a whole but as individuals stain 
less deeply that the peripheral ones (Figs. F, G). 
The ganglion is enclosed in a rather dense connective-tissue 
sheath, which stains pink with fuchsin. In this sheath, and some- 
times outside of it, a variable number of scattered nerve cells are 
found, which seem to be a part of the central system. I found no 
nerve cells in the gland, but in almost every specimen at some point 
in the series, gland cells and ganglion cells seemed so completely 
mingled that it was hard to separate the two areas, a condition 
such as that described for other tunicates by Mercazr (1899 and 
1900). 
The cells which compose the ganglion are of various sizes from 
very small ones with almost no cytoplasm to rather large ones 10 
or 20 x in diameter. Small and large sorts are found together both 
in the center of the ganglion and in the dense masses near the 
surface. With methylen-blue and eosin stains, the cells appear 
mostly unipolar, and spherical or pear-shaped; but there are cer- 
tainly many cells with several processes, although very often one of 
these is much longer than the others. Very probably the cells which 
