246 THE SPOROZOA 



or less, and is effected in a manner very similar to that described above 

 (p. 211) for Coccidia. The movements of the merozoites are similar to 

 those of the sporozoites, but less active, and they may also show feeble 

 amoeboid movements. 



Opinions still differ considerably as to the true structure and 

 significance of the very characteristic ring -stage of the endoglobular 

 parasite. Some authorities regard it as truly ring-like in structure, the 

 result of the union of two horn-like outgrowths or pseudopodia. Amongst 

 recent writers this view is supported by Ewing [66]. But most 

 authorities consider the ring-like appearance as merely the optical section 

 of a vesicular structure. Even then it is far from clear whether the 

 vesicle is a vacuole or whether it is simply the enlarged nucleus, distended 

 by fluid nuclear sap and containing a relatively small quantity of 

 chromatin. The latter alternative is, according to Argutinsky [61, 1902] 

 and others, the true interpretation of this stage. Argutinsky considers, 

 however, the distended condition of the nucleus to be merely the artificial 

 result of unsuitable methods of preserving these parasites as microscopic 

 objects. He states that if blood-films are treated with fixatives before 

 being dried, nothing is seen of any " ring-forms," but the nucleus appears 

 as an even spherical mass of chromatin, not surrounded by any clear space 

 intervening between it and the protoplasm of the body ; if, on the con- 

 trary, the blood-film be dried before fixation, according to the method of 

 procedure most commonly in vogue, the result is a deformation of the 

 tiny parasite, producing the ring-like appearance. On the other hand, 

 Schaudinn [94a] gives a very different account of the ring-form in the 

 case of the tertian parasite. He finds that it does not occur in the develop- 

 ment of the gametocytes, but that it is a constant stage in the growth 

 of the schizonts. In the latter case it appears in the youngest amoebulae 

 as a vacuole situated close to the nucleus. The vacuole grows rapidly in 

 size, causing the parasite to have the form of a signet-ring, as commonly 

 described, the nucleus being on one side of the ring. When the ring- 

 stage is fully developed it is difficult to say whether the vacuole is still 

 closed in, above and below, or whether the body does not become truly 

 ring-like. Schaudinn regards this vacuole as nutritive in function, con- 

 nected with the absorption of food-substance, and serving to increase the 

 body-surface of the parasite ; its appearance close to the nucleus supports 

 this interpretation ; and its presence in young schizonts, but not in young 

 gametocytes, is correlated with the fact that the former grow twice as fast 

 as the latter. 



According to Billet [64], the endoglobular malarial parasite has 

 constantly at a certain stage of its growth an elongated form, coiled round 

 within the corpuscle. Billet terms this the Gregariniform stage, and 

 considers that it represents the haemogregarine phase of the Gymno- 

 sporidia. It remains to be seen to what extent such a stage is of constant 

 occurrence. According to Argutinsky's figures and descriptions [61, 1902] 

 of the tertian parasite, it frequently has " an elongated vermiform shape," 

 which is to be regarded as merely one of the many forms which result 

 from its very great amoeboid activity, and this author shows that even the 

 nucleus shares, to a certain extent, in the changes of body-form. Schau- 



