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94 Proceedings of the Eoyal Physical Society. 



body is distinguishable through a very considerable number 

 of stages, and is finally represented by a little red bulge 

 (Figs. 41, 42 a and h). The two fine red strands forming the ' 

 junction between the preflagellar body and the kinetonucleus 

 are exceedingly persistent, and can sometimes be seen in the 

 fully developed adult trypanosome (Figs. 38-42 I). ( 



Slight variations in the development of the flagellum occur, 

 but they are of a very insignificant character. Occasionally 

 the preflagellar bodies appear to be thinner (Fig. 33), and 

 assume the flagellar appearance at an earlier stage. 



This has, I think, occasionally to do with the stain, which 

 may only pick out part of the apparatus. The demonstration 

 of these preflagellar bodies is often a very difficult matter, on 

 far the larger number of otherwise quite satisfactory pre- 

 parations they appear simply as a little white patch in 

 the protoplasm at the anterior end of the animal. Workers 

 studying trypanosomes are familiar with the difficulty fre- 

 quently experienced in getting the flagella to take the stain. 

 The preflagellar bodies show an even greater obstinacy and 

 capriciousness in this matter. Very satisfactory prepara- 

 tions may, however, be obtained by the ordinary Laveran and 

 Giemsa procedures. I 



Briefly to sum up this question : The flagella appear to be 

 developed from a pair of arrested mitotic figures developed 

 out of the distal of the two segments into which the original 

 kinetonucleus divides. | 



At what I have called the " Herpetomonas or Crithidial 

 stage," the kinetonucleus lies in front of the trophonucleus, 

 and the flagellum projects straight out. Before division 

 takes place, two flagella may be distinctly seen, both in the 

 living condition and in stained preparations. The move- 

 ment of the live Herpetomonas-like forms with one flagellum 

 is interesting. The flagellum is lashed about rather stiffly, 

 and the body of the creature, which shows none of the 

 rippling motion characteristic of so many trj^panosomes, is 

 drawn after it. In fact, a less trypanosome-like movement 

 could hardly be imagined. It is most fascinating to observe 

 the fine gradations in external shape and in the method of 



