INTRACELLULAR DIGESTION OF INVERTEBRATES. 101 



HaeckeP, for example, has observed this in Echinoderms, and 

 Geddes^ in the lymph cells of Lumbricus, in MoUusks, and in 

 Pagurus and other Decapods. These observations are entirely 

 confirmatory of the views of those observers who regard giant 

 cells as true plasmodia, due to a fusion of several distinct cells. 



Another example of the formation of mesodermal plasmodia 

 (as I shall henceforward call giant cells) was seen in an 

 Asterigera, which had had a drop of human blood injected 

 beneath the skin. Most of the corpuscles were ingested, each 

 by one or two separate cells ; but the larger clots were each 

 surrounded by several cells, which fused to form plasmodia. 

 These latter, though loaded with masses of corpuscles, were yet 

 able to move by means of large pseudopodia. The nuclei were 

 so obscured that it was impossible to observe them in the living 

 state ; I therefore treated the plasmodia with alcohol and borax 

 carmine, finally clearing with oil of bergamot. By this treat- 

 ment the nuclei came out distinctly ; they were all situated in 

 the peripheral part of the plasmodiura, the centre of which was 

 filled with great balls of fused blood-corpuscles. 



We should conclude, from the above-described observations, 

 that when mesoderm cells are confronted with a large mass of 

 food material, which they cannot devour singly, they fuse into 

 a plasmo.dium, which eats up the whole available food. This is 

 not, however, invariably the case. When the mucous tissue of 

 Phyllirhoe was filled with large bodies, such as the boiled eggs of 

 Sphserechinus granularis, or boiled cells from the cotyledons 

 of peas, I could see no formation of plasmodia. Shortly after 

 the introduction of these bodies into the tissue, small amoeboid 

 cells collected round them in great numbers, and remained for 

 several days — till the death of the animal — closely surrounding 

 them, but without the slightest sign of fusion one with 

 another. The cells surrounding the tissue of the pea re- 

 mained inactive during the whole time ; for, being unable to 

 perforate the thick cellulose wall, they could not commence in- 



' • Radiolarien,' p. 103, Anus. 2. 



* "Ou the Coalescence of Amoeboid Cells into Plasmodia," ' Proc. Roy. 

 See.,' 1880, p. 252, pi. V. 



