438 On a Species of Coccidium infesting Pericheeta. 



The division of the cell-contents into a large number of 

 sporoblasts is a fact of some little importance with regard to 

 the affinities of the Goccidia^ to which group the present 

 species seem without doubt to belong. 



The oviform psorosperms, including Coccidium and 

 Schneider's genus Orthospora^ as well as Eimeria and Cyclo- 

 spora^ which differ in having a circular form, are distin- 

 guished from other Gregarines (1) in being intracellular 

 parasites, for the greater part of their life and even in the 

 latest stages parasitic in the tissues of their host ; they are 

 never free-living : (2) in the fact that they only produce a 

 limited number of spores — one to four. 



In Klossia and Benedenia (which Schneider does not regard 

 as distinct from Klossia) the number of spores is much greater ; 

 but they agree with the other Coccidiidte in their mode of life 

 and are generally referred to that family. In the phenomenon 

 of their sporulation, which may perhaps be related to their 

 greater size, they agree with other Gregarines, and they form 

 therefore an intermediate group between Coccidium &c. and 

 the Monocystidse. 



This affinity between the Coccidiidce and the Monocystidce 

 is rendered closer hy the fact that Coccidium perich^tas, which 

 is a typical oviform Coccidium, produces a large number of 

 spores like the free-living Gregarinidce. It also resembles 

 certain of the latter^ e. g. Gamocystis, in the great development 

 of the outer cyst-7nembrane. 



With regard to the Coccidium from Pericheeta novce- 

 zelandice I have observed the formation of a large number of 

 sporoblasts (fig. 16) ; but I have not noticed the thick outer 

 cyst-membrane. As has been already stated, the formation of 

 spores in the Coccidium from Pericheeta armata does not advance 

 pari passu with the development of the outer membrane ; it 

 may be therefore that I did not succeed in observing any 

 individuals in which the outer cyst-membrane was developed, 

 but that there were others not observed by me in which it was 

 to be found. 



I have stated at the commencement of this paper that in 

 both species of Perichmta the Coccidium occurred in the body- 

 cavity ; I certainly met with the Coccidium from Perichoita 

 novce-zelandice in this situation in company with a large 

 species of Gregarine which I have described elsewhere*. I 

 cannot be so certain about Pericheeta armata^ as the intestine 

 of the worm from which I obtained my specimens was rup- 

 tured. In both cases, however, the Coccidia may very 



* " Note on a new Gregarine," Proc. Zool. Soc. 1888, pt. iii. 



