210 THE SPOROZOA 



but the patient is by no means immune against the consequences 

 of a fresh infection from without. 



In other Coccidia the schizogony may be wanting altogether, or 

 be more limited in its duration, and in such cases the parasites are 

 very harmless and inflict little or no injury upon their hosts. This 

 is especially true of those found in Mollusca, commonly infesting, 

 as has been said, the kidneys in these animals. 



(b) Morphology and Evolution. The complete life-cycle of Coccidium 

 schubergi has been worked out so thoroughly and in such detail by 

 Schaudinn, that it may serve very well as a type of the whole 

 order, the chief variations that are known to occur being specified 

 afterwards. 1 



Coccidium schubergi is parasitic in the intestinal epithelium of 

 Lithobius forficafus, where it is commonly found in company with 

 two other species, Coccidium lacazci (Labbe), and Added orata, A. 

 Schn. The infection of the centipede is started by its accidentally 

 swallowing cysts with its food. The cyst-wall is then dissolved by 

 the digestive fluids, the four spores each split lengthways, and the 

 sporozoites, of which two are contained in each spore, are liberated 

 in the digestive tract. Each sporozoite proceeds at once to attack, 

 and to penetrate within, an epithelial cell of the host. 



The free sporozoite is a minute, sickle-shaped body 15-20/x in length, 

 4-6 /A in breadth (Fig. 49, a and b, and Fig. 50, a). The anterior 

 extremity is more pointed and refringent, the posterior end more rounded. 

 The finely-granulated protoplasm, which is not limited by any distinct 

 cuticle, contains a spherical nucleus placed near the middle of the body, 

 visible in life as a clear spot, and showing after preservation and staining 

 a number of chromatin granules, lodged in an alveolar linin framework, 

 but no special central corpuscle, nucleolus, or karyosome. The sporozoite 

 performs active movements of various kinds. In the first place, it 

 changes its form, as a whole, either by bending the body like a bow, and 

 then straightening it out again, or by ring-like constrictions of the body 



1 In the following account of the life-histories of Coccidia, the terminology employed 

 for the various stages is that which has been gradually evolved by numerous authors 

 during recent years, and to which Schau<linu has put the finishing touches. The chief 

 departures here from Schaudinn's nomenclature are, that the term "zygote" is used 

 instead of " copula," and that the term " oiicyst " is understood to mean the membrane 

 rather than the contents. In many recent memoirs some of these special terms are 

 employed in different senses, making the descriptions often very difficult to under- 

 stand. The commonest instance of this is the use of the term " macrogamete " to 

 denote what should be termed a female merozoite or macromerozoite (see p. 223). 



Some author.-, amongst whom Lang and Grass! are especially prominent, make use 

 of a quite different terminology, proposed originally by Haeckel. The non-sexual 

 schizogony is termed monogony, as being a case of reproduction by single individuals, 

 without conjugation, and the schizonts are termed immonts. The gametocytes are 

 termed gattietogenous mononts, the formation of the gametes being regarded as a 

 special case of monogony. The zygotes or sporonts are termed amphionts, formed 

 as they are by the coming together of two individuals, aud the sporogony is termed 



