﻿Trypanosome found in Pontobdella. 



95 



locomotion that are to be seen on a single slide of live 

 material where this process is going on. As the animal 

 assumes the trypanosome condition by the lengthening of 

 the body and the migration posteriorwards of the kineto- 

 nucleus, the creature as a whole becomes more lissom, and 

 more of the movement is executed by the flexion of the 

 body and less by the lashing of the flagellum. Cf. Figs. 

 39-42 l. 



In the Crithidial stages the arrangement of the granules is 

 worthy of notice, in so far as these, when present, may lie in 

 either the flagellate or the non-flagellate part of the creature 

 pretty well indifferently, though they are perhaps more 

 frequent in the non-flagellate end. 



Even in the fully-developed trypanosome, the granules 

 may sometimes lie posterior not only to the trophonucleus 

 but also to the kinetonucleus. In other cases they are pretty 

 evenly divided throughout the whole creature, or may be 

 in the flagellate end. It may be mentioned in passing 

 that granules are of very varied occurrence in these 

 trypanosomes. 



The development which has just been traced seems to me 

 to be a strong argument against the division of the Hsemo- 

 flagellates suggested by Dr H. M. Woodcock in the Quarterly 

 Journal of Microscopical Science, April and June 1906, into 

 Monadina and Heteromastigina, a division based on the 

 conception that the anterior flagellate end of the Herpeto- 

 monadine forms corresponds to the posterior non-flagellate 

 end of the trypanosomes. Dr Woodcock thus derives the 

 trypanosomes not from a Herpetomonad ancestor by the 

 migration posteriorwards of the kinetonucleus, but from a 

 bi-flagellate form of the type of Trypanoplasma borrelli by 

 the loss of the anterior flagellum. He therefore separates 

 Trypanomorpha noctuce from all the other trypanosomes. I 

 do not wish here to enter into the vexed question of the 

 ancestry of Hsemoflagellates. It would be rash, as well as 

 futile, to discuss this point at the present time, and this is 

 more especially true where such a phylogenetically eclectic 

 form as a trypanosome is concerned. I would only wish to 

 observe that while trypanosomes have features reminiscent 



