COCCIDIIDEA 



137 



to the Coccidium type, in others according to the Eimeria type. It therefore was 

 reasoned that in this case it was not a question of two species belonging to different 

 genera living side by side, with a different mode of development, but of one species, 

 in the life of which both forms of development occurred alternately. 



This interpretation of facts was combated especially by A. Schneider (1892) and by 

 Labbe, but has, nevertheless, proved true, apart from the circumstance that Schuberg 

 succeeded in discovering the hitherto unknown Coccidium form in the intestine of 

 the mouse ; and that, moreover, Leger confirmed the fact that there are no Arthro- 

 poda in which Eimeria are not found together with coccidia. The question was 

 finally settled by experiments made by Leger with the coccidia of Scolopendra 

 cingulata, by Schaudinn and Siedlecki with those of Lithobius forficatus, and by 

 Simond with the coccidia of the rabbit. On Simond's suggestion the sickle-shaped 

 germs corresponding to the sporozoites, which are formed by endogenous sporula- 

 tion, are generally termed merozoites ; and in accordance with Schaudinn's 

 suggestion, those individuals which form merozoites are termed schizonts, and 

 those which produce spores are called sporonts. In contradistinction to sporogony 

 (exogenous sporulation), the term schizogony (endogenous sporulation) is used. 



The more minute examination of these processes at last led to the discovery of 

 sexual dimorphism, of copulation and of alternation of generations in the coccidia. 

 Schuberg was the first to consider the possibility of copulation in coccidia ; in 

 addition to the formations which now are termed merozoites, he observed very 

 diminutive bodies (" microsporozoites ' ; ) in the coccidia of the intestine of the mouse, 

 which were able eventually to copulate. Labbe confirmed this observation in some 

 of the species, and Simond expressed the opinion that bodies termed "chromato- 

 zoites " occurred in all coccidia. Copulation itself was then observed by Schaudinn 

 and Siedlecki (1897). The copulating bodies were termed gametes. As, however, they 

 differed considerably one from the other, the males were called microgametes (i.e., 

 the microsporozoites of Labbe and the chromatozoites of Simond) and the females 

 macrogametes. After copulation was completed sporogony took place, and in the 

 cycle of development of one species this regularly alternated with schizogony (asexual 

 multiplication). Schaudinn in 1900 described in detail the life-cycle of Eimeria 

 {Coccidhini} schubergi. 



The recognition of this unsuspected complicated process was bound to effect 

 reforms in the classification of the coccidia ; and all the forms that had been 

 regarded as developmental stages (Eimeria, etc.) had to be reconsidered. 



Occurrence. The Coccidiidea in their mature condition usually 

 live within the epithelial cells of various organs, and by choice inhabit 

 those of the intestine and of its associated organs. They also occur 

 frequently in the excretory organs of mammals, birds, amphibia, 

 molluscs, arthropods, and may also be found in the testes and vas 

 deferens, but the statement that they live in hen's eggs, as well as 

 in the oviducts of fowls, has not been confirmed. 1 Some species 

 inhabit the nuclei of cells, others live in the connective tissue, but 



1 Notwithstanding the progress made during the last decades, the ova of helmmthes 

 and more particularly of trematodes, have been mistaken for Coccidia. Thus Poschinger 

 {Zool. Anz., 1819, ix, p. 471) and Gebhard (Virchoirfs Arch., 1897, No. 147, p. 536) mistook 

 the ova of Distoma turgidum, Brds., for Coccidia. Podwyssotzki (Centralbl. f. allg. Path., 

 1890, i, p. 135) made a similar error with the ova (and vitelline sacs) of a species of Prostho- 

 gonimus (Distoma ovatum of the authors) ; von Willach (Arch. f. wiss. u. prakt. Thierheilk., 

 1892, xviii, p. 242) mistook the ova of a nematode for Coccidia. 



