434 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
sented in text-figure B show not only that the trumpet cavity winds 
from side to side but that the part to the right, the anterior vestibule, 
is more dorsal than the part to the left, the posterior recess or terminal 
sac. It also shows that the cavity of both vestibule and trumpet tube 
opens out to the exterior by narrow slits. The same can be shown 
to be true of the recess in certain planes. The granular material in¬ 
dicated in these cavities of the annulus was sperm while the granular 
mass just external to the annulus and ventral was part of the sperm- 
plug, that is, the wax-like mass protruding from the orifice. 
The general character of the annulus and adjacent organs is again 
shown in text-figure C which is a cross section but not quite vertical. 
Above, it shows the large muscle masses right and left of the ventral 
nerve-cord which is cut across the long commissure between the gan¬ 
glia of the fourth and fifth thoracic somites. 
Below the nerve-cord is the small sternal artery embedded in con¬ 
nective tissue which forms the general mass of the annulus. The 
Fig. C. 
annulus is the large mass of connective tissue projecting downward 
and covered by exoskeleton that thins off right and left into the thin 
exoskeleton of the non-elevated surface of the body. This thin lateral 
exoskeleton is easily cut to remove the annulus as a conical mass. In 
the middle of the annulus is a large cavity with very thick exoskeletal 
walls; this is the vestibule of the trumpet and its irregular form is due 
to the fact that it is cut anteriorly, and somewhat obliquely from side 
to side. The exterior depression beneath this cavity is the anterior 
