114 Wituiam A. Hinton, 
in methylen blue and eosin. Another most serviceable method was 
to fix with Fremming’s fluid and after sectioning to stain with iron- 
or copper-hematoxylin. 
General form of the ganglion. 
The ganglion is roughly cylindrical. It is imbedded in the 
mantle between the oral and atrial siphons. A long neural gland, 
found on its ventral side (Figs. A, D, E), is more or less closely 
applied to the nerve center and usually extends its whole length or 
even farther in the direction of the animal’s oral end. It is from 
this end that a duct of greater or less extent may be followed to 
such a ciliated funnel as has been described and figured by Junin 
(1881), MercaLr (1900), and others. The length of this duct from 
the end of the ganglion to the funnel differs considerably in the 
various specimens examined. There is also some variation in the 
position and extent of the duct in the region of the gland. In some 
individuals this tube, or branches from it, may be traced from the 
wall of the ganglion itself. That is, it has communication with the 
nervous tissue similar to that described and figured by SHELDON 
(1887) in Clavellina. This author suggests that the ciliated pit and 
duct are for the purpose of aerating the brain. Mercazr (1899 and 
1400) calls attention to the close relationship between gland and 
ganglion in tunicates, and in some of his figures shows relations 
which might be regarded as histological connections between this 
duct and the brain. 
The chief branches of the ganglion run off from its two ends 
and take a rather dorsal direction. The usual figures of the gan- 
glion in simple tunicates show only such branches. In some specimens 
of 7. niyra, in which the stain was not differential, only these larger, 
Fig. A. Drawing of the ganglion and gland of Tunica nigra, from a recon- 
struction. The oral end is up, the ganglion is turned slightly to one side, so that 
more of the gland, on the ventral side, is seen than would be shown in a strictly 
lateral view. A duct from the gland shows at the oral end. At various places at 
the end of the ganglion the stumps of nerve trunks are seen. 17:1. 
Fig. B. Drawing from a reconstruction of a ganglion of Tunica nigra, looking 
down upon the dorsal surface. Several of the chief nerve trunks are shown, some 
being a little exaggerated in the drawing, especially the median ones at the lower 
or atrial end. 17:1. 
Fig. C. Drawing from a model of a portion of the atrial end of a ganglion 
in ventral aspect. To facilitate comparison with Fig. B, the atrial end is down, 
though the shading of the figure is thereby reversed. The cut surface shows a 
small dorsal median branch cut lengthwise. Other branches are also shown. A 
ventral view of this part of the ganglion is given to show especially a small lateral 
fold which extends toward the median plane. 17:1. 
