THE H.EMOFLAGELLATES. 315 



although, doubtless, comparable functionally with the simi- 

 larly-named organella of a Trypanosome, seems most probably 

 not homologous with the latter as regards origin and struc- 

 ture. Although it is generally well-developed (cf. fig. 64 a, 

 b), Schaudinn in no instance mentions the observation of any 

 thickened edge comparable with the flagellar border of the 

 membrane of a Hfemoflagellate.^ 



On the other hand, again, the more Spirochfeta-like a 

 Trypanosome is, the narrower and less developed is the 

 undulating-membrane; indeed, in such cases the flagellar 

 border is the most conspicuous part of this organ- 

 ella, the membrane being often recognisable only with 

 difficulty (cf. T. ziemanni [fig. 32], T. johnstoni [fig, 

 51], other slender Trypanosomes, and, lastly, Spironema 

 pallidum, below). 



The writer is more inclined to Laveran and Mesnil's idea 

 of the "membrane" of a Spirochaeta as a general ecfco- 

 plasmic investment surrounding the body (see above, p. 312) ; 

 such a sheath might well appear, as in Schaudinn's figures. 

 - (c) The character of the nucleus in both S. balbianii and 

 S. plicatilis differs considerably in two respects from that 

 of a Trypanosome. In the first place, it is (particularly in S. 

 balbianii) very diffuse, more akin, in short, to the "distri- 

 buted" type associated with Bacteria, and, in the second 

 place, there is not the well-marked distinction between 

 kinetic and trophic chromatic elements which is so charac- 

 teristic of a Hfemoflagellate. The writer does not think, 

 with Perrin and Schaudinn, that the axial thread represents 

 the locomotor nucleus of a Trypanosome. It may be kino- 

 plasmic, but it certainly appears to serve as a ground-work 



^ As mentioned above, Perrin considers tliere is such a chromatic border 

 in "T." balbianii ; but neither Laveran and Mesnil nor Leger noticed such 

 a feature in their examination of this form. The writer cannot help thinking 

 to some extent with Mesnil that Perrin has been rather too preoccupied with 

 the idea of realising, in this parasite, the ancestral Trypanosome. Mesnil 

 considers that some of the stages described by Perrin (e. g. the formation of 

 "male gametes" and the encystment process) represent really involution 

 forms. 



