60 



PROTOZOA. 



infest the epithelium of the alimentary canal may cause the death of 

 their host. They encyst within the cell which they inhabit, and 

 their protoplasm gives rise to coated spores. Conjugation is un- 

 known, and there are no cuticular structures until the cyst-wall is 

 formed. 



The cyst-wall may be thin, in which case sporulation takes place in the same 

 host, and the germs (falciform bodies) are set free to reinfest the same host 

 (endogenous sporulation), or it is thick and double-contoured, in which case the 

 cyst, on the breaking down of iffe cell-host, falls into the alimentary canal and 

 is ejected with the faeces. In the latter case the sporulation (exogenous) takes 

 place outside the host, and the germs are set free after the spores have entered ;i 

 new host. 



FIG. 46. Coccidiwn oviforme from the liver of the rabbit (from Wasielewski, after Balbiani). 

 a and b, young cocciclia in epithelial cells of the bile duct, the cell-nucleus lies in the upper 

 process of the cell host ; c, encysted form ; d and e, contraction of the protoplasm to a 

 sphere ; y, h, i, spore-formation ; k, ripe spore with two falciform young and a residual body. 



In some Coccidiidea only one spore* is produced; in such cases the whole 

 animal becomes the spore, and its cyst-wall the spore case. In the rest the 

 contents of the cyst divides into two or more spores (leaving as usual a residue) 

 which acquire cuticular coats. In all cases the contents of the spore gives rise 

 to the falciform bodies (one or more, leaving a small unused residue) which 

 are the germs or young. 



Tribe 1. Monosporea. The whole contents of the cyst forms only one spore, 

 and the spore has no spore-case distinct from the cyst- wall. Orthospora A. Schn. , 

 spore with four falciform bodies, intesc. epithelium of Triton; Eimeria, Schn., 

 numerous falc. bodies, intest. epithelium of mouse, frog, fishes, myriapods, etc. 



* The archespore of Labbe seems to be merely the spore before the formation 

 of the spore-case. The sporozoites are the bodies which proceed from the spore ; 

 they are called in the text falciform bodies, and are the young forms. In 

 Labbe's nomenclature a spore which produces one falciform body is called 

 monozoic ; that which produces two falciform bodies is called dizoic, and so on 

 to polyzoic. 



