LIPE-CYOLE OF " OYSTOBIA " IRBEGULAEIS (mINCH.). 35 



vessel and had eight uiiclei. I have also obtained several 

 examples from this situation which possessed numerous 

 nuclei (figs. 39 and 40) ; in the latter case nuclear multipli- 

 cation was already far advanced. In all these instances the 

 partition separating the two associates is persistent, and the 

 animals had not, so far, made the slightest attempt to encyst. 



Taking the majority of cases, where the Gregarines have 

 become evaginated and spherical, they are surrounded, of 

 course, by the peritoneal epithelium, which shuts them off 

 from the coelome and serves, indeed, as the outer wall of the 

 cyst. The parasites are bounded internally by a fairly thin 

 membrane, corresponding to the originally limiting membrane^ 

 Avhich can now be spoken of as an endocyst {en., figs. 41, 44). 

 I doubt whether any other membrane, equivalent to an ecto- 

 cyst such as we find in D. schneideri, is secreted as a rule 

 in C. irregularis; at all events, I have only rarely seen 

 anything resembling one. A thick, protective cyst-wall is 

 not necessarjr, the evaginated wall of the blood-vessel serviug 

 equally well for the purpose of enclosing the developing 

 sporoblasts. In rare instances, however, when the parasites 

 are in the swollen evaginations described below, and not 

 closely surrounded by the peritoneal epithelium, the cyst- 

 membrane does appear to consist of two parts, there being a 

 pale, homogeneous layer outside the endocyst, which perhaps 

 corresponds to an ectocyst {ect., fig. 44a and h.y It is not 

 nearly so well marked, however, as in C. minchinii, and in 

 typical cysts attached to the blood-vessels there is no sign of 

 such a layer. 



In sections of sporulating cysts which only contain, as yet, 

 numbers ol: nuclei scattered throughout the cytoplasm (fig. 41), 

 there is, between the endocyst and the coelomic epithelium, a 



1 Gregarines iu which the cytoplasm is becoming segregated (i. e. the out- 

 lines of the sporoblasts becoming visible) are rather liable to shrinkage, 

 especially when in this unusual position in tlie membrane anteriorly. In these 

 cases the cyst- membrane is often folded on itself in places (fig. iib), the 

 folds (/) appearing somewhat like strings of attachment under a low power; 

 the membrane has been unable to shrink equally with the cytoplasm as the 

 latter became retracted. 



