94 DR. ELTAS METSCHNIKOFP. 



are usually embedded in the protoplasm itself ; but are some- 

 times surrounded by a vacuole indicating the occurrence of 

 some digestive process. The ectodermal granules are iden- 

 tical with those existing in the endoderm and in the gastric 

 cavity of the larva, showing that they are not to be considered 

 as products of the metabolism of the organism itself. In 

 fact, we are forced to believe from what has been said that 

 the larvse of an Actinia, when in the body of the parent, are 

 commensal parasites, living on the food taken in by the mother. 

 If the larvae be removed from the mother, and put into water 

 containing carmine in suspension, the carmine granules are 

 eaten by the ectoderm cells, being seized by means of short 

 pseudopodia extended from the free surface. 



After the development of the gastric pouches, the number of 

 foreign particles in the ectoderm is much smaller. Young 

 larvae, still in the body of the mother, in whose ectoderm no 

 granules can be seen, retain the power of ingesting carmine 

 granules, especially in the ectoderm of the tentacles and disk. 

 It is exceedingly difficult to follow the further history of in- 

 gested granules, whether in ectoderm or endoderm ; but it is 

 hardly conceivable that they should be ingested with any other 

 object than that of subsequent absorption. 



As a further example of ectodermal nourishment, may be 

 cited the ovarian ova of those animals whose generative cells 

 are ectodermal — for example, those of Tubularia, and, accord- 

 ing to KorotnefF, of Hydra. In the first-named animal I have 

 seen the young amoeboid ovum eat and digest the neighbouring 

 follicular cells. KorotneflP^ asserts, without giving any proof 

 of his statement, that during the winter the young ectoderm 

 cells of Hydra devour the older ones. 



II. — Intracellular Ingestion and Digestion by 

 Wandering Mesoderm Cells. 



While the taking up of nutriment by ectoderm cells can only 

 be observed in rare and exceptional cases, nothing is easier 



» ' lu his llussian memoir ou Myriothela aud Hydra.' Moskow, 1882, 

 p. 43. 



