748 SUMMARY OF CURRENT RESEARCHES RELATING TO 



with the especial object of studying its intracellular digestion. He 

 finds that 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. Thus in the 

 gastric tube itself the oral cells produce a secretion, the cells of the 

 mid-gastric layer are inactive, while those of the proximal or ingestive 

 region are the only ones that exhibit intracellular digestion. During 

 life there were observed in this portion green unicellular organisms, 

 large Euglena-like forms, or smaller Protococci. The cells appeared to 

 be naked, and to have pseudojiodia-like processes ; they unite to form 

 a meshwork in which there are large intervening spaces. Secretion- 

 cells are also to be found in this layer, and these are swollen and 

 granular when the cells of the oral region ajjpear to have been shed 

 and have left intercellular spaces. On the other hand, the oral 

 secretion-cells are richly developed when the cells of the proximal 

 region are exhibiting the phenomena of intercellular digestion. 

 Professor Lankester infers that this is seen in a state of comparative 

 fasting, in which such small bodies as may be ingested by the 

 endoderm of the proximal region are proportionally valuable to the 

 organism. The other condition would apjjear to obtain when relatively 

 large prey has been taken into the gastric cavity. 



In some observations on its development,* Professor Lankester 

 compares it with Geryonia, and he thinks that Haeckel's observation, 

 according to which the sub-umbrellar cavity is formed as a closed 

 space between two layers of the ectoderm, is correct. He points out 

 that this sub-umbral sac corresponds with the so-called stomach of 

 the Ctenophora and its opening with their so-called mouth. In both 

 cases it is lined by ectoderm, and developes quite independently of 

 the endodermal cells, which give rise to the stomach and canals of 

 the Hydromedusae on the one hand, and to the infundibulum and 

 canals of the Ctenophora on the other. 



Medusae and Hydroid Polyps Living in Fresh Water. — 

 Mr. Komanes, wi-iting f with reference to the remarks of Prof. Agassiz, 

 which we quoted at p. 968 of vol. iii., says that he has made no 

 experiments or statements with reference to the effects of brachish 

 water either in estuaries or elsewhere, his experiments consisting 

 merely in suddenly transferring Medusae from sea water to perfectly 

 fresli water. 



Porifera. 



Propagation of Sponge by Cuttings. | — The 'Journal of the 

 Society of Arts ' contains an abstract of an account given by Dr. E. v. 

 Marenzeller of the efforts made by the Austrian Government to 

 improve sponge cidture in the Adriatic, from which the following is 

 condensed. 



Prof. 0. Schmidt expressed a conviction that if a perfectly fresh 

 sponge were cut into suitable pieces, and these were again placed in 



* Quart. Journ. Micr. Sci., xxi. (1881) pp. 194-201 (1 pL). 



t Ibid., pp. 162-.5. 



X Journ. yoc. Arts, xxix. (1881) pp. 592-4. 



