DIGESTION AND ENDODERM OF LIMNOCODIUM. Ibe | 
regions of this Medusa’s body in specimens preserved in osmic 
acid. 
The series of questions which arise in connection with this 
phenomenon of intra-cellular digestion are so numerous and 
important that it is quite certain that the most complete study 
of the endoderm of the various regions of the digestive tract is 
necessary before the phenomenon can be rightly appreciated. 
The following considerations, amongst others, are those which 
naturally present themselves to an observer as indications 
directing his inquiries. 
PRELIMINARY CONSIDERATIONS. 
1. Supposing it to be established that some of the endoderm 
cells in Hydroid and Anthozoan polyps are capable of ingesting 
solid food particles, the question arises whether this is an occa- 
sional and accidental phenomenon, or whether it is a normal 
and definitely fixed function of such endoderm cells. 
2. The question also occurs as to whether all the endoderm 
cells have this property, or whether it is limited to certain groups 
of these cells, whilst a distinct kind of activity (possibly similar 
to that of the gastric cells of other animals) is assigned to other 
cells in the same animal. 
3. Further, it is of fundamental importance to ascertain what 
becomes of food particles ingested by ameboid endoderm cells. 
Are these particles digested by these cells as food particles are 
by an Ameeba? or are they again ejected unchanged. 
4. Supposing the food particles to be digested—that is to say, 
dissolved and converted into diffusible peptones or analogous 
substances—what becomes of such peptones? Are they simply 
retained by the endoderm cell for its own nutrition ? or are they 
passed by that cell away from its surface to subjacent cells, 
which thus are nourished by a process of diffusion? or, again, 
are the products of digestion returned by the endoderm cell to 
the alimentary tract, and carried thence by its ramifications, 
as a nutrient fluid, into various regions of the body ? 
5. Are there any special kinds of food particles which are 
ingested in the solid form by certain endoderm cells, whilst other 
food materials are dissolved and distributed by diffusion, in the 
same way as are albuminoids and carbo-hydrates, by the ali- 
mentary organs of Vertebrata. Is there any ground for sup- 
posing that the ingestion of fats in a particulate form by 
Vertebrata is a survival of the intracellular digestion now esta- 
blished as occurring in Ceelentera and Planarians ? 
When we take into consideration the structure of Hydra it 
seems possible that the sole nutrition of the ectoderm cells is, 
by means of the products of digestion, elaborated by endoderm 
