104 DE. ELIAS METSCHNIKOFF. 



ingestion by the mesoderm cells of Bipinnaria, we see that 

 they are completely absorbed. Within the cell they swell up 

 and become clearer ; the hsemoglobin is then dissolved out, 

 and finally the whole corpuscle disappears. (I need hardly 

 say that corpuscles which have not been eaten do not undergo 

 this series of changes.) The corpuscles of Discoglossus, 

 injected into Phyllirhoe, behave somewhat differently. The cell- 

 body, and the nucleus, of such a corpuscle, becomes somewhat 

 irregular in shape after ingestion ; a crumpling process goes 

 on, which results in the breaking up of cell-body and nucleus 

 into several fragments. At this stage the central part of the 

 mesoderm cell becomes slightly coloured. The whole process 

 resembles the resorption within the so-called blood-corpuscle- 

 containing cells of Vertebrates, which must really be regarded 

 as a process of feeding on the part of a mesoderm cell.^ 



Milk injected beneath the skin of Bipinnaria and Phillirhoe 

 has the same fate. The milk spherules are eaten by wander- 

 ing cells, lose their shining appearance, and break up into 

 small granules, which are distributed throughout the cell 

 substance. I have not yet observed any noticeable alteration in 

 ingested starch grains. 



In order to ascertain whether the mesoderm cells exercised 

 any choice in the particles they absorbed, I injected mixtures 

 of different kinds. For example, I filled the mucous tissue 

 of a Phyllirhoe with a mixture of milk and indigo, carmine 

 and starch grains — nutritious and nseless bodies together — 

 and I found that all these bodies were equally absorbed, 

 some cells eating all four kinds of food at the same time. 

 From this it would be supposed that the mesoderm cells ate 

 everything provided for them, without power of distinction. 

 The following experiment, however, seems to contradict such a 

 view. On injecting into a Phyllirhoe living ovarian ova from a 

 Sphserechinus granularis, it was found that neither 

 young ovarian cells, nor ripe ova which had extruded polar 

 bodies, were eaten by the mesoderm cells ; on the contrary, 



^ G. Langerhaus " On the Resorption of Extravasations and the Formation 

 of Pigment within them," ' Virchow's Archiv,' 1870, Bd, 49, pp. 81, et seq. 



