36 H. M. WOODCOCK. 



rather fibrous layer, staining with the plasma stain (/. I., 

 figs. 41, 44 c). This is not in any way comparable to an 

 ectocyst, but is, on the contrary, a layer of the spongy tissue 

 of the blood-vessel, somewhat altered in character, being 

 drawn out and tending to disappear. Later on, when the cyst 

 is full of sporoblasts and spores, it is no longer recognizable. 

 By this time the enclosing wall is very thin ; it consists only 

 of the peritoneal covering outside, and, next internally, the 

 endocyst, which has now become extremely delicate and difii- 

 cult to make out where it is applied to the epithelial layer. 

 Sometimes, however, the endocyst has shrunk slightly away 

 from the latter, and it is then seen more readily (fig. 44 d) ; 

 at other times, again, especially in ripe cysts, it has quite 

 broken down and vanished. Indeed, in many of my sections 

 through spore-containing cysts, however carefully cut, the 

 delicate peritoneal wall itself is ruptured in places. 



The cyst shown in fig. 42 was in an evaginated blood- 

 capillary in the membrane already mentioned (p. 12) as run- 

 Tiing from the ring-canals to the body-wall, and conveying 

 the radial vessels. It appears to have very thick walls, but 

 this is due to the fact that these evaginatious are swollen and 

 expanded and partly filled with vascular fluid (Jl.) more or 

 less coagulated by fixation. There is no question whatever 

 of this being a thick, gelatinous ectocyst, for scattered here 

 and there are seen amoebocytes and blood-corpuscles [x., x.). 

 The wall itself {u\) is very faintly stained, and consists of the 

 usual loose tissue, here excessively spongy and having an ill- 

 defined limit internally; indeed, it is difficult to say in places 

 where the wall ends and the cavity begins. The Gregarines 

 in this position are much freer than those in the ordinary 

 evaginated cysts, which are closely invested by the fibrous 

 layer above described; and this fact probably accounts for the 

 development of an ectocyst, albeit only slight, in such cases. 



C. minchinii. — In encysted adults of C. iniuchinii 

 attached to the muscles there is, as yet, no sign of any 

 cyst-wall apart from the delicate limiting membrane. This 

 is usually difficult to make out owing to the thick nuclear 



