Apsilus and other American Rotifer a. By Dr. A. G. Stokes. 271 
portion of this thick, collar-like muscle bears pendent from its central 
region, and apparently communicating with its central passage, a 
long membranous tubular body, which sways with the movements of 
the anterior stomach (proventriculus), and with the flow of its con- 
tents. This tube (figs. 1 and 2) probably has the same purpose as 
the similar structure observable in the crop of Floscularia; but I 
have not been able to observe this, although I have several times seen 
the Rotifer take food. The process was accomplished too rapidly to 
exhibit the details after the food-particle had passed into the oeso- 
phageal ring. 
The proveutriculus is a thin- walled sac, provided with several 
muscular bands, and in vigorous, almost constant motion, especially 
when the coronal cup is expanded. Its external surface, or that 
•surface bathed by the fluid of the general body-cavity, is furnished 
with a coat of somewhat scattered cells, oval, nucleated, and usually 
Ailed with dark-bordered granules and refractive bodies, probably oil- 
drops. These cell-contents are noticeably increased when the pro- 
ventriculus is well supplied with food and the processes of digestion 
are apparently active. They thus seem to have some important 
function to perform in connection with the solution of the food or 
with its absorption. That the proventriculus positively has digestive 
power, is proved by the fact, which I have several times seen, of the 
presence within it of the mastax from one or more Rotifers, with 
the soft parts entirely gone, the chitinous framework of the part alone 
remaining. I have likewise several times observed the presence within 
the proventriculus of the empty lorica of a Rotifer, its protoplasmic 
contents having been dissolved out, only the indigestible lorica and 
the enclosed framework of the mastax remaining. 1 do not know 
that such chitinous remains ever pass the mastax into the posterior or 
true stomach ; I have never seen such remains there nor in the 
intestine, but I have seen at least one large and indigestible object 
ejected through the oesophageal ring, after what may be called a 
mighty effort to get rid of it. I have seen, not Apsilus bucinedax, it 
is true, but Apsilus bipera, thus eject through the oesophageal ring a 
Cypris which had been rotated about the proventriculus, apparently 
much against its will, for it was tightly closed within its shell, and 
after its ejection remained dazed for a few moments, when it separated 
the valves of its shell and sailed off into the open water. That what 
I have called the proventriculus has digestive power, there can be no 
doubt. 
The mastax at the fundus of the anterior stomach is large, massive, 
and complex. The trophi differ conspicuously from the same parts in 
Apsilus lentiformis Metsch., as shown by figs. 5 and 6, the former 
being the trophi of A. lentiformis. Fig. A is from A. bucinedax , but, 
complex as it appears, I am inclined to think that 1 have either mis- 
interpreted some portion or have not seen it all distinctly, as there 
are at times glimpses of another curved, rod-like piece of chitin at the 
u 2 
