THE SPOROZOA 205 



upon their affinities with Gregarines. A year later Kloss gave the first 

 thorough account of the life-cycle, in the case of the form infesting the 

 snail, subsequently named Klossia helicina by A. Schneider. Kloss's 

 work was also the first proof of the existence of these parasites in Inverte- 

 brates. The endogenous life-cycle was first described by Eimer in 1870, 

 in the form infesting the mouse, termed by him Gregarina falciformis; 

 but later (1875) made by Schneider the type of a new genus, Eimeria. 

 Henceforth these organisms became known as "egg-shaped psoro- 

 sperms " (eiformige Psorospermien, Psorospennies oviformes), and their 

 affinities with the Gregarines received general recognition. In 1879 

 Leuckart greatly increased our knowledge of the Coccidian parasites of 

 the rabbit, and introduced for them the new generic name Coccidium, in 

 the second edition of his well-known treatise upon human parasites. 

 From this time onwards these parasites were commonly known aa 

 " Coccidia " a word often used in an extremely vague sense by writers 

 whose zoological knowledge is defective, and by whom it is sometimes 

 employed in a sense practically synonymous with the older word " psoro- 

 sperms." 



In the eighties our knowledge of the forms of Coccidia and their life 

 cycles was steadily increased, chiefly by the labours of Aime" Schneider, 

 and in more recent years by Labbe. In the last decade of the nineteenth 

 century a vast amount has been written about Coccidia on account of the 

 connection suspected to exist between them and cancer, but this work has 

 been for the most part barren of results, contributing little to extend 

 our knowledge either of cancer or of Coccidia. It is in this period, 

 however, that the complete life-cycle has been gradually worked out by a 

 number of observers. An alternation of generations was first suggested 

 by L. and R. Pfeiffer, whose ideas met with the most vigorous criticism, 

 but a double life- cycle has now been demonstrated to be of almost 

 universal occurrence amongst Coccidia. Towards the end of the nine- 

 teenth century, also, sexual reproduction has been observed and accu- 

 rately studied in a number of forms. The new century commences with 

 an exhaustive monograph by Schaudinn upon the complete life-history 

 of the forms infesting the centipede Lithobius, a publication which marks 

 an epoch in the investigation not only of Coccidia but of Sporozoa 

 generally, and completes our knowledge of a most fascinating chapter in 

 natural history. 



(a) Occurrence, Habitat, Effects on their Hosts, etc. The Coccidia 

 are an abundant group of the Sporozoa, but appear to be confined, 

 in the matter of hosts, to three great phyla the Arthropoda, 

 Mollusca, and Vertebrata. 1 In the last named they are found 



1 Exceptions are the Coccidian parasites discovered by Caullery and Mesnil in the 

 gut of Capitetta capitala [126] and other Polychaete worms [129a]. Since only the 

 schizogony was observed, the systematic position of these forms could not be deter- 

 mined ; they remain for the present, therefore, without any generic or specific 

 designation. On the other hand, these authors are of opinion that the alleged 

 Coccidian parasites in Perichaeta, described by Beddard (Ann. Mag. Ifat. Hist. (6), 

 ii. 1888, p. 433), are nothing more than segmenting eggs of Nematodes. It is 



