16 n. M. WOODCOCK. 



commnnication vvitli a blood-capillai-y) contains some of tlio 

 peculiar amoobocytes (am.), laden with excretory pigmented 

 o-rannles. The bending- inwards of the wall at h, and the 

 proliferation of nuclei where it is applied to the Gregarine 

 are also well shown. The cytoplasm of the part still un- 

 covered has mostly shrunk away from the limiting-membrane; 

 this is probably due to the fixing. Fig. 17, PI. 2, shows a small 

 portion of another invaginated parasite and its covering, 

 highly magnified. The cytoplasm is dense and granular, 

 and closely surrounded by the inner layer of epithelium. 

 Here, also, the lumen of the stalk (/) contains many amoebo- 

 cytes, which are very common in the blood-capillaries of both 

 Cu cum aria and Holothuria; the peripherally-situated 

 nucleus {n) of each is deeply stained. 



Finally, in PI. 2, fig. 13, we have a Cystobia, which has 

 thrust its anterior end, as a long finger-like process, into a 

 rather narrow vascular cord; into this the animal appears to 

 be trying to penetrate. This parasite was found in a spirit- 

 fixed Cucumaria, and its outer, free end is rather shrunk 

 and irregular, as also are the outlines of the nuclei. The 

 section along c — D (fig. 14a) shows the Gregarine every- 

 where enclosed by the double epithelial layer. X is a portion 

 of the process in the strand, which is also cut through, e 

 being the outer and p' the inner invaginated wall. Lum. 

 is the lumen, more or less filled up with spongy tissue, with 

 here and there a few amoebocytes {am.). Fig. 14/; is a 

 section drawn along the line A — B, and passing through 

 the tip of the protuberance (p). This is still enveloped by a 

 cellular layer, the cells being thickly aggregated at one 

 side. 



The above is the only instance I obtained showing such a 

 modification of the Gregarine's shape, and I doubt whether 

 it frequently occurs. I am more inclined to think that the 

 parasites, after a preliminary invagination of the ctploinic 

 epithelium, are rather enclosed and overgrown by tliis and 

 the underlying connective tissue of the immediate neighbour- 

 hood than that they themselves actually penetrate deeply 



