226 



THE HAEMOFLAGELLATES 



transition between binary fission and the other characteristic method 

 of T. lewisi, namely, segmentation or rosette-formation (Fig. 21). 

 The chief difference is that, in the latter, no parent-individual is 

 recognisable, the segmentation being equal and giving rise to a 

 rosette of equal daughter-Trypanosomes. 



The small parasites resulting from either of these modes of 

 division (Fig. 21, E) differ from typical adults by their stumpy, pyri- 

 form shape, the position of the kinetonuclens near the flagellar end 

 of the body, and the absence, during the first part of their youth, 

 of an undulating membrane. At this period they have a somewhat 

 Herpetomonas-like aspect. These young individuals can them- 



FIG. 21. 



A-D, segmentation 



(rosette- formation) in T. leitrisi ; in C nuclear division has finished and 



the daughter-nuclei (of lx>th kinds) have taken up a superficial position, while the cytoplasm 

 has become lobulated at the periphery, prior to the formation of the daughter-Trypanosomes. 

 E, daughter-individual ; F, one dividing, x 1750. (After L. and M.) 



selves multiply by equal binary fission, giving rise to little 

 fusiform parasites ; and, with growth, these gradually assume the 

 adult appearance. 



6. THE LIFE-CYCLE OF TUYPANOSOMES 



It may be safely said that this remains, even to-day, one of the 

 most difficult and most debated questions among the whole of the 

 Protozoa, in spite of the amount of work, of one kind or another, 

 which has been contributed to the subject during the last few 

 years. When the present writer compiled his Review of the 

 Haemonagellates (3) some years ago, Schaudinn's remarkable 

 observations had been, to all appearance, amply corroborated in 

 various directions by the testimony of the Sergents (77), Billet 

 (4, 5), Brumpt (9), Le"ger (50), and Rogers (94) ; in short, the 



