380 THE PROTOZOA 



cross.* T. parva is the parasite of " East Coast fever " of cattle in 

 Africa. Other species have been described from the fallow-deer and 

 from Cephalolophus grimmi. 



(3) Nicollia, Nuttall. Oval or pear-shaped parasites with peculiar 

 iiuclear structure (see below), and with quadruple division, pro- 

 ducing a figure at first like a fan, then like a four-leaved clover. 

 One species, N. quadrigemina, from the gondi, Ctenodactylus 

 (Nicolle, 746). 



(4) Nuttallia, Franca. Parasites oval or pear-shaped (not rod- 

 shaped) ; multiplication-forms like a cross. N. equi, of equine 

 piroplasmosis ; N. herpestidis, of a mongoose (Herpestes ichneumon). 



(5) Smithia, Frana. Pear-shaped forms, occupying the whole 

 diameter of the corpuscle, not in pairs ; quadruple multiplication 

 in the figure of a cross. S. microti from Microtus arvalis. 



Future research will, no doubt, determine the value of these 

 generic distinctions, some of which seem to rest upon a somewhat 

 slender foundation. 



As is evident from the foregoing classification, the form of the para- 

 site varies considerably in different species, and even in the same 

 species. In many cases the body may show amoeboid changes of 

 shape, and may throw out long pseudopodial processes. The two 

 principal types of form of the full-grown parasite are the pear- 

 shaped and the bacillary forms ; but the smaller parasites may be 

 ring-like, with the nucleus excentric, and placed near the margin 

 of the body in some cases. The relation of these forms to one 

 another, and their significance in the life-cycle, are not clear, but the 

 annular forms appear to be young stages of either the pear-shaped 

 or bacillary forms. Kinoshita claims to be able to distinguish 

 indifferent (schizonts) from sexually-differentiated forms (sporonts) 

 (compare Theileria, p. 382, infra}. 



The minute structure of the body is very simple, since the cyto- 

 plasm has as a rule no enclosures except the nucleus, which is 

 .single. In some cases, however, the cytoplasm may be vacuolated 

 to some extent, and in the ring-like forms has a large central 

 vacuole. The nucleus itself appears to be of a simple type of 



* A confusion has arisen between two parasites very similar as regards the 

 appearances they present in the blood, but differing in every other respect namely, 

 Theileria parva, the true parasite of " East Coast fever " of cattle, and Babesia 

 (Piroplasma) mutans, also found in cattle. In both parasites alike the charac- 

 teristic cross-forms appear in the blood. In Theileria parva, however, the cross- 

 forms are an aggregation of four distinct gametocytes (see p. 382, infra) which 

 have invaded the same corpuscles, while in Babesia mutans the cross-forms are 

 produced by quadruple fission of an ordinary multiplicative individual ; this 

 difference has the consequence that, since the gametocytes of T. parva are not 

 capable of further development in the blood of the ox, direct inoculation of blood 

 from an infected to a healthy ox does not produce an infection in the latter, as 

 happens always when a healthy ox is inoculated with blood containing Babesia 

 mutans. The diagnosis of the genus Theileria given by Franca would appear to 

 apply to B. mutans rather than to T. parva. See especially Gonder (739). 



