THE H^MOFLAaELLATES. 277 



(fig. 29). It is not found, on the contrary, in binary longi- 

 tudinal fission/ whicli, it must be remembered, is by far the 

 most prevalent and most typical mode of division in natural 

 circumstances. In such cases there is no indication whatever 

 of a Herpetomonadine facies (cf. figs. 23, 25). Hence it 

 seems to the writer that this association of the nuclear 

 elements bears some relation to their rapid multiple division 

 during segmentation, perhaps facilitating the complex me- 

 chanical processes which apparently occur. 



Now the juxtaposition of the two nuclear bodies of itself 

 confers a semi-Herpetomonadine aspect on an individual ex- 

 hibiting it. When further, as frequently in this rosette type 

 of multiplication, the daughter-nuclei travel towards the peri- 

 phery, doubtless to assist in the segregation of the general 

 cytoplasm into the individual portions," the resemblance to a 

 Herpetomonad is much increased. We have, in short, what 

 may be termed a " pseudo-Herpetomonadine " form developed 

 (cf. figs. 28, 29). The absence or rudimentary character 

 of the undulating membrane is sufficiently explained by the 

 position of the kinetonucleus and the very short portion (if 

 any) of attached flagellum present in consequence, and need 

 not be further considered. 



To sum up, therefore, this difficulty with regard to the 

 variation in position of the kinetonucleus does not seem in- 

 superable ; on the other hand the biological considerations, 

 as well as the other morphological characters above men- 

 tioned appear to oifer far greater objections in the way of 

 the Herpetomonadine theory. Nevertheless, this does not 

 necessarily imply that all the species included below uuder 

 Trypanosoma are derived from a Trypanoplasmatine an- 

 cestor. Some almost certainly ai-e, e.g. T. brucii and T. 



' This refers, of course, to adult Trypanosomes as such ; parasites exhibit- 

 ing the " pseudo-Herpetomonadine " form may divide while retaining it 

 (see above, p. 240). 



^ With reference to the arrangement of the parasites in the multiplica- 

 tion-rosettes found in cultures, which cannot be regarded as entirely normal 

 see above, p. 241. 



