392 THE PROTOZOA 



such forms on his Plate XXII., Figs. 2-4 small intracorpuscular forms, more 

 or less Leishmania-like, ivithout pigment, and with, apparently, distinct tro- 

 phonucleus and kinetonucleus. 



It is not necessary to deal with Schaudinn's statements concerning Leuco- 

 cytozoon further than has been done above (p. 370). It is now as certain as 

 anything can ever be in such matters that Leucocytozoon has nothing whatever 

 to do with either trypanosomes or spirochsetes. The six forms of biood- 

 parasites of the Little Owl may be regarded as belonging to five species, 

 namely: A proteosoma (1), a halteridium (2), a trypanosome (3 and 4), a 

 leucocytozoon (5), and a spirochaete (6). Of these five, it is probable that only 

 the proteosoma, the trypanosome, and possibly the spirochsete, can develop 

 in, and be transmitted by, a gnat ; the halteridium and the leucocytozoon 

 require, probably, quite different intermediate hosts. If, therefore, a Culex 

 were fed on an owl containing in its blood halteridia and leucocytozoa abun- 

 dantly, and trypanosomes and spirochsetes in scanty numbers, the first two 

 parasites might be expected to die out after the ookinete-stage, while the 

 trypanosomes, and possibly the spirochsetes, would multiply, and thus produce 

 very easily the impression that they were derived from the intracorpuscular 

 parasites. 



Even less cogent for the theory of Haemoflagellate affinities than the argu- 

 ments deduced from the development of Hsemosporidia are those based on 

 the development of Haemoflagellates. Thus the schizogony of Schizotry- 

 panum discovered by Chagas has been compared to that of a malarial parasite, 

 and has been adduced seriously as an additional proof of the alleged affinities 

 between trypanosomes and haemamceba?. But " schizogony : ' that is, repro- 

 duction by simple or multiple fission without concomitant sexual phenomena, 

 occurs throughout the whole range of the Protozoa, and affords no proof 

 whatever of genetic affinities. Those who bring forward such an argument 

 must surely have forgotten that the word " schizogony " was originally 

 coined by Schaudinn for the non-sexual multiplication of Trichospharium 

 sieboldi, a marine Rhizopod (p. 181). 



2. Cytological Data. The theory of the Hsemoflagellate affinities of the 

 Hsemosporidia has led to the most laborious and painstaking efforts to discover 

 in the body of each and every Hsemosporidian parasite, in at least some of 

 its phases, a second nucleus, the homologue of the kinetonucleus ; and any 

 little granule, however minute, that can be coloured like chromatin is pro- 

 claimed triumphantly to be the inevitable kinetonucleus, or any streak of 

 similar staining properties to be a flagellum. 



Consider first by itself the case of a cell in which, in addition to the nucleus, 

 there is seen a grain which, by some particular dye, is stained in a manner 

 similar, or nearly so, to the chromatin of the nucleus. This is not by itself 

 a decisive proof that the grain in question is chromatin, since, as pointed out 

 above, other grains may take up so-called " chromatin-stains " ; the body 

 in question may therefore be chromatin or some other substance. If it be 

 chromatin, it may be a chromidial granule extruded from the nucleus ; or it 

 may be a body of the nature of a karyosome, situated close to the edge of the 

 nucleus, or possibly, in some cases, where the nucleus has no limiting mem- 

 brane, a little way from the main mass of the nucleus ; or it may be a true 

 kinetonucleus. If it be not chromatin, it may be a centrosome or blepharo- 

 plast ; or a grain of metachromatinic substance, such as volutin ; or, lastly, some 

 other kind of metaplastic body. There are therefore many possible alterna- 

 tives before a grain that stains like chromatin can be identified definitely as 

 being a kinetonucleus and nothing else. 



What are the criteria by which a grain that stains like chromatin can be 

 identified as a kinetonucleus, to the exclusion of other possible interpretations 

 of its nature ? In the first place, according to modern views (see p. 288, 

 supra, and compare especially Rosenbusch, 505), a kinetonucleus is not a 

 simple granule, mass or lump of chromatin, but it is a true nucleus with 

 centriole, karyosome, and a nuclear cavity, actual or virtual, containing 

 nuclear sap at least, if not peripheral chromatin also. Secondly, a kineto- 



