122 PROFESSOR E, RAY LLANKESTER, 
cells, such products passing through from the endoderm cells to 
ectoderm cells by osmosis. And we have definite observations 
of Metschnikoff (in the case of Ctenophora) upon the passage of 
carmine particles, away from the endoderm cells which took them 
up, into mesoderm cells lying beneath them, which favour the 
notion of such a passage. It may, however, be noted that the 
carmine particles do not appear in this case to have been 
digested—that is, chemically changed and dissolved—and hence 
the passage of the particles in question is a phenomenon similar, 
in essential respects, to the passage of fat particles unchanged 
through cells on the surface of the intestinal villi of Vertebrates 
to subjacent cells and cell spaces. 
On the other hand, when we try to bring the structure of the 
Meduse, with their elaborate gastro-vascular canal system, into 
relation with the facts of intra-cellular digestion, we find it 
impossible to admit that the nutrition of the organism can be 
carried on by the mere osmotic passage of nutrient matters from 
those cells which are active as intra-cellular digesters to subjacent 
cells. Metschnikoff has observed that in many Celentera the 
intra-cellularly digestive cells are limited in number and position, 
and this fact I can fully establish by my observations on Limno- 
codium. Hence the regions in which subjacent cells can be 
nourished by superjacent intra-cellularly digestive cells is ex- 
ceedingly limited. The products of the digestive activity of the 
intra-cellularly digesting endoderm cells are in all probability, 
in the Medusee, returned to the alimentary canal, and carried on 
by the agency of the gastro-vascular canals into the remoter 
parts of the organism. 
Bearing in mind these considerations we may proceed to an 
examination of the endoderm of the gastric and gastro-vascular 
cavities of Limnocodium. 
INTRA-CELLULAR DIGESTION IN THE PROXIMAL REGION OF THE 
Gastric TUBE OBSERVED DURING LIFE. 
The manubrium of Limnocodium is a somewhat quadrangular 
tube, which depends during life below the margin of the um- 
brella. Its cavity, the stomach, presents a considerable difference 
in the structure of its lining cells, the gastric endoderm, in 
different regions. Where the four angles of the stomach-tube 
are inserted into the umbrella they are slightly produced, and 
give rise to the four radiating canals. The enlarged angles of 
the stomach are lined by peculiar cells,in which I observed an 
intra-cellular digestion to be proceeding during the observation 
of living specimens. In Plate VIII, figs. 1 and 2, two drawings 
of this intra-cellularly digestive endoderm, taken from living 
specimens, are reproduced. The cells are seen to form a widely- 
