MUSEUM OF COMPARATIVE ZOOLOGY. LE 
quently pointed out, must be to carry the particles of food from the bases 
of the tentacles towards the mouth. 
The mouth is limited on the side towards the anus, and separated 
from the cloaca by a fold, which may be designated the inner lip. This 
represents the organ often referred to as the epistome, —a term which 
implies an homology with the organ of the same name in Phylactole- 
mata. ‘This organ is of greatest size in Rhabdopleura and Loxosoma 
among Endoprocta, where it is elevated far above the general level of the 
floor of the atrium. It is less marked in the Pedicellinide. In Urna- 
tella it is not at all evident, because its upper edge is not higher than 
the roof of the rectum which forms the actual floor of the atrium be- 
hind. If, on the contrary, the cloaca extended underneath the rectum, 
as it does in the Pedicellinide, causing a great space between it and 
the intestine, and thus making the roof of the dntestine the floor 
of the atrium, the inner lip would appear as a very prominent organ 
(cf. Fig. 18). 
On the outer edge of the mouth, and forming the “ outer lip,” is a 
prominent horizontal fold of the oral part of the atrium (Fig. 18, loph. 
atr.). This fold extends aborally, running parallel with, and forming the 
outer wall of the “ atrial groove” (Fig. 19). The fold gradually becomes 
less pronounced towards the aboral aspect of the atrium until (in Fig. 
18) it forms only a slight swelling of the atrial wall over the rectum. 
Alimentary Tract. — As in other Endoprocta, so in Urnatella one can 
distinguish four regions in the alimentary tract: cesophagus, stomach, 
intestine, and rectum. The wall of the alimentary tract is composed 
throughout of a ciliated epithelium, except in the so called hepatic cells 
of the upper wall of the stomach. In this exception Urnatella agrees 
with other Pedicellinide, but for Loxosoma Harmer makes no such 
exception. 
I find a highly refractive basement membrane lying at the base of 
the digestive epithelium. This stains deeply in hematoxylin, so that it 
can be seen with a low power as a distinct line surrounding the alimen- 
tary tract. Such a condition, described by Nitsche (’69, p. 19) for 
Pedicellina, has been denied by Ehlers (90, p. 72) to exist in Asco- 
podaria. 
There is an indication of a specialized intestinal (sphincter) muscle 
surrounding the opening leading from intestine to rectum, as well as at 
the anus. The structure in question, which appears in section (Fig. 18, 
spht.) as highly refractive and deeply staining areas on either side of 
the opening, seems to lie in the epithelial wall of the alimentary tract. 
