THE H^MOSPORIDIA 393 



nucleus when present is a permanent cell-element which, like the principal 

 nucleus, divides when the cell divides, and is propagated by fission equally 

 with the cell itself. Thirdly, and this is the most important criterion of all, 

 the kinetonucleus is in relation with a flagellum during at least some phases 

 of the development, though for a time the locomotor apparatus may be 

 temporarily absent, its existence indicated only by the kinetonucleus during 

 resting phases. 



The smaller chromatinic body of Leishmania may be cited as an example of 

 a body which fulfils these conditions, and which can be identified unhesita- 

 tingly as a true kinetonucleus, homologous in every way with that of a try- 

 panosome. But with the alleged kinetonuclei of Hsemosporidia the matter 

 stands quite otherwise. It is not possible to discuss fully here every separate 

 instance, but a few typical examples of such bodies may be dealt with 

 briefly. 



In female halteridia and leucocytozoa (Pig. 158), a large grain is seen by 

 the side of the nucleus, and often interpreted as a kinetonucleus. Until this 

 body has been shown conclusively to be related in some phase of the life- 

 history to a flagellum, it is far simpler to regard it as a karyosome which, 

 like that of the merozoites of Addea (Fig. 153, F), is excentric, or possibly 

 extranuclear in position ; assuming, that is, that the body in question is a 

 true chromatinic nuclear element. 



In the merozoites of Proteosoma, Hartmann (675) has discovered a flagellum- 

 like ( j>rocess at the anterior end, arising from a grain which he regards as a 

 kinetonucleus (" blepharoplast " in the German use of the term), thus con- 

 firming certain obiter dicta of Schaudinn (132, p. 436) with regard to the mero- 

 zoites and sporozoites of the tertian parasite. It may be pointed out that the 

 rostrum of the sporozoites of Gregarines appears to be a perfectly similar 

 structure, which very possibly represents a rudimentary flagellum arising 

 from a true blepharoplast of centrosomic nature. Hartmann' s discovery is 

 therefore more proof of the affinities of proteosoma with other Telosporidia 

 than with Haemoflagellates. 



The supposed kinetonuclei of piroplasms have been mentioned above ; the 

 entire absence (pace Hartmann) of flagellated stages throughout the life- 

 cycle make it impossible to accept any such interpretation of the nature of 

 these granules so highly inconstant in their occurrence. 



Lastly it should be mentioned that Schaudinn, and recently Hartmann, 

 have maintained that the microgametes of halteridia and other Haemosporidia 

 have the structure of a trypanosome. Inasmuch as Schaudinn also pointed 

 out the great structural similarity between trypanosomes and spermatozoa, 

 this point might not count for much, even if it were true ; unless the Metazoa 

 also are to be classified amongst the Binucleata, a conclusion which, indeed, 

 seems to follow from the nuclear theory of Hartmann and Prowazek (63). 

 In objects of such extreme minuteness, however, statements ascribing to them 

 complicated details of structure must be regarded with great scepticism until 

 thoroughly substantiated. It is a sufficient warning of the need of caution 

 to bear in mind the controversy that has raged over the question of the minute 

 structure of spirochaetes, with regard to which Schaudinn was obliged to 

 retire from the position he took up at first namely, that their structure was 

 similar to that of a trypanosome. 



3. Possible Transitional Forms. The parasite of kala-azar was originally 

 described by Laveran under the name Piroplasma donovani,* in the belief that 

 it was a true piroplasm ; and many writers have been struck by the external 

 similarity of the two parasites, in spite of the difficulty in finding in Piroplasma 

 a satisfactory representative of the constant and definite kinetonucleus of 

 Leishmania. In fact these two genera are often cited as the connecting link 

 between Haemoflagellates and Haemosporidia, and are supposed to indicate 

 the course of evolution whereby serum-parasites of the first type became 



* On the other hand, the parasite of Oriental Sore was first described by Wright 

 under the name Helcosoma tropicum, and referred to the Microsporidia. 



