150 PROFESSOR E. RAY LANKESTER. 
early contribution to the subject of intra-cellular digestion and 
the comparative physiology of digestion in general, which I do 
not doubt is about to be investigated with new vigour and 
interest, in consequence of Metschnikoff’s researches. 
SuMMARY. 
1. The cells of the endoderm of the gastric tube and gastro- 
vascular canals differ very considerably in form and in the 
chemical metamorphosis of its substance in different regions. 
2. The nuclei are alike in all as to size and form, excepting 
in the cells of the abumbral wall of the marginal canal and the 
similar cells of the endoderm of the genital pouches. 
3. These latter are angular, close-set cells, with dense block- 
like deposits in their protoplasm concealing the nucleus. 
4, The cells of the radial canals are close set and ciliate with 
sparse, hyaline protoplasm. 
5. The endoderm of the gastric tube is divisible into three 
regions: a, the oral, J, the mid-gastric and ¢, the ingestive or 
proximal. 
6. Only the cells of the proximal region exhibit intra-cellular 
digestion. 
7. The cells of the oral region produce a secretion by their 
development as secretion cells (goblet cells of Claus). 
8. The cells of the mid-region are inactive. 
9. The cells of the proximal region appear, under certain 
circumstances, as an open meshwork giving off amceboid pro- 
cesses, by means of which they take in solid food particles. 
10. Under the same circumstances the secretion-cells of 
the oral region are richly developed and in place. 
11. Under other circumstances the cells of the oral region 
appear to have been, to a large extent, shed, leaving inter-cel- 
lular spaces. 
12. When this is the case, the secretion-cells of the proximal 
are swollen and granular, and the inter-cellular spaces of the 
meshwork obliterated. 
13. It is inferred that the latter circumstances are the result 
of the taking into the gastric tube of relatively large prey; 
whilst the former condition is one of comparative fasting, in 
which such small food bodies as may be ingested by the endo- 
derm of the proximal region are proportionately valuable to the 
organism. 
ADDENDUM ON THE ENDODERM OF THE TENTACLES. 
In Plate X, fig. 3, a surface view is given of one of the 
smallest sized tentacles, for the purpose of showing the mode in 
which the thread-cells are clustered in groups upon its surface. 
