Species o/'CoccIdium infesting Perlchfeta. 437 



that the outer cjst-membrane, instead of disappearing as the 

 cyst ripens *, not onlj persists, but increases greatlj in im- 

 portance. I have observed various stages in the increase in 

 thickness of this membrane, which are illustrated in figs. 9, 2, 5, 

 6, 12, 15 ; it finally comes to project beyond the two poles of 

 the cyst for a very considerable distance (fig. 15), sometimes 

 equal or nearly equal to the length of the cyst. Although 

 this membrane increases so greatly in thickness, especially at 

 the two poles, it remains of a very delicate consistency and is 

 extremely transparent. It bears no little resemblance to the 

 thick transparent outer cyst-membrane of Oamocystis and 

 CIepsidrina'\. Occasionally (fig. 15) concentric lines, perhaps 

 indicating the deposition of successive layers, are visible. 



It is important to observe (fig. 15) that in these advanced 

 stages the micropyle has not any relation whatever to the 

 outer cyst-membrane, which is a further argument against 

 regarding this structure as an aperture. 



It often happened that two cysts, each limited by its own 

 inner membrane, were enclosed partly (fig. 8) or entirely 

 (fig. L'3) in a common outer membrane. 



Sporvlation. — In Coccidium oviforme the first preliminary 

 to sporulation is the condensation of the protoplasmic contents 

 of the cyst into a rounded mass. This I have not discovered 

 in Coccidium perichcetce J or, rather, I have not observed any 

 great differences in this particular between various individuals 

 "with a still undivided mass of protoplasm. The condition, 

 however, of the material (preserved in alcohol) is probably 

 responsible for this ; but in any case there does not appear to 

 be any formation of a membrane enclosing the spores, as in 

 Cyclospora \. 



Various stages in the division of the protoplasm are shown in 

 figs.4,3,8,9,13, 12,15, and these stages are an almost unbroken 

 series, showing the division into a large number of sporoblasts. 

 The increase in number of the sporoblasts does not bear any 

 definite relation to the increase of the outer cyst-membrane. 

 In some individuals the outer cyst-membrane had attained 

 to a high development, while the protoplasmic contents of 

 the cyst were still undivided (fig. 7). On the other hand, 

 figs. 8 and 9 illustrate two individuals in which the outer cyst- 

 membrane was inconspicuous, while the cell-contents had 

 already divided into several masses. I have not succeeded in 

 tracing the formation of spores any further than to this point. 



* Biitschli, loc. cit. pi. xxxvii. figs. 11 a and b, 



t Schneider, " Contributions a I'lustoire des Gregariens &c.," Arch. 

 Zool. Exp. t. iv. (1875)., 



X Schneider, loc. cit. pi, xxii. figs. 2.3-38. 



