DIGESTIVE PROCESSES IN PLANAKI^. 
213 
Alcyonaria, lead her to conclude that large food bodies are 
rapidly broken up into small particles, and in some cases 
apparently acted on by some digestive ferment in the coelen- 
teron of the zooids before being ingested by the cells of the 
ventral mesenterial filaments, and that “ we have evidence 
in the Alcyonarige as in the Madreporaria of an intercellular 
digestion by the secretion of a digestive fluid in the coelenteron 
of the zooids, as well as an intra-cellular digestion which 
occurs throughout the coelenterates.” 
Jordan (’07) has come to similar conclusions on the diges- 
tion in Actinia, and says that in them digestion is both inter- 
and intra-cellular. He put little paper bags containing fibrin 
in the gastric cavity of some Actinia, and found that the 
contents were digested although the bags remained intact. 
His results are in agreement with those of Krukenberg. 
Even in Hydra, according to Hadzi (’00), an appreciable 
amount of extra-cellular digestion takes place, the food being 
slightly predigested in the lumen before being ingested by 
the pseudopodia of theendoderm cells. 
We need not be surprised then tliat in the more highly 
organised Planarian, digestion is not entirely intra-cellular. 
The alteration which the fat-globules undergo in the 
columnar cells is characterised by very marked alterations in 
their staining reaction. At first they are deep black owing 
to the action of the osmic acid in the fixing fluid in which the 
animals were preserved (figs. 1 and 2). 
Each globule is enclosed in a vacuole. Within half an 
hour after feeding, some of the globules at the free end of 
the cell become paler, changing from black to grey, and then 
brown. Within two hours after feeding (figs. 2, 4, and 5) the 
change had proceeded a great deal further. The black 
reaction to osmic acid is no longer present, and the fat takes 
the less basic of the two basic stains, the fuchsin, till eventu- 
ally it is only stained by the acid cytoplasmic stain, the 
orange G. (figs. 4, 0, and 7). A vacuole is no longer visible, 
and eventually the fat-globules are incoi’porated in the sub- 
stance of the cytoplasm. 
