158 BULLETIN OF THE 
The most prominent objects in the anterior chamber, however, are the 
four big cells which, in two pairs, an anterior and a posterior, fill almost 
the entire space above the brain, and send their processes ventrad into 
its substance. They are the cells which Fewkes (’85, Expl. of Plates, 
p. 208) designates as “ova (?)," and which Birger (91, p. 646) sup- 
posed to be salivary glands. Neither hypothesis has much in its favor, 
and I shall present evidence which I believe shows them to be clearly ner- 
vous, i. e. ganglion cells. Accordingly, the description of their structure 
and relations will be deferred until the consideration of the ganglion 
cells in the brain. 
4. Bopy Cavity, 
The main body cavity extends from the posterior face of the partition 
which cuts off the anterior chamber to the extreme posterior end of the 
body. It varies much in size in different individuals (Plate II. Figs. 23- 
26, Plate IV. Fig. 58, and Plate VIIT. Fig. 96) and can hardly be said 
to have a definite form. It is smallest in immature individuals, and 
most capacious after sexual maturity. It differs somewhat from the 
body cavity of the anterior chamber. The latter, as has been shown 
already, is lined, in great part at least, by a peritoneal membrane, but the 
general body cavity shows no trace of such a lining. The protoplasmic 
ends of the muscle cells terminate at variable depths, thus giving it an 
irregular boundary, which shows no sign of an endothelium. In the 
body cavity one finds neither dissepiments nor mesenteries ; the intes- 
tine floats free, or at regular intervals in its course is grown fast to cells 
in some part of the body wall. 
In the male one always finds a sac more or less developed hanging 
from the dorsal line, and varying in form and structure. This will be 
more fully described under the sexual organs, to which it unquestion- 
ably belongs. 
There is often a small amount of coagulated substance in the body 
cavity which contains scattered corpuscles similar to those of the ante- 
rior chamber. They are very pale, entirely unstained, and of a spongy 
texture. One finds various sizes, and their origin from the protoplasmic 
ends of the muscle cells has already been maintained. They are by no 
means abundant, and the amount of coagulum found in the body cavity 
is also small. In addition to these one always finds in the body cavity 
of the male free spermatozoa in greater or less numbers. In all of the 
females obtained the body cavity was nearly or quite filled with eggs. 
