OKGANISATION 



317 



expressed similar views, and considered the two types of trypanosome 

 generically distinct. Woodcock (1906), in discussing the phylogeny of the 

 trypanosomes, arrived at the conclusion that two distinct families are 

 represented (Trypanosomatidse and Trypanomorphidse), one including 

 heteromastigine forms evolved from trypanoplasm ancestors originally 

 parasitic in the vertebrate intestine, and the other including herpetomona- 

 dine forms evolved from insect or invertebrate flagellates. In the former 

 the flagellar end is posterior, while in the latter it is anterior. There 

 seems to be, however, no sound argument to support this view. Repre- 

 sentatives of both Woodcock's groups are culturable, and in these cultures 

 they all tend to revert to flagellates of the insect type— viz., leishmania, 

 leptoraonas, and crithidia forms — a fact which speaks strongly in favour of 



B 



Fig. 152. — Agglomeration of Trypanosomes and Trypanoplasms by their 

 Posterior Ends as a Kesult of the Action of Sera ( x ca. 1,300). (A, 



AFTER LaVERAN AND MeSNIL, 1912; B, AFTER SCHINDERA, 1922.) 

 A. Trypanosoma lewisi. B. Crijplohia helicis. 



the similarity of their origin. In his genus Trypanomorpha, Woodcock 

 places Trypanosoma noduce and probably some of the avian and mamma- 

 lian trypanosomes, while the genus Trypanosoma includes all other forms. 

 The phenomenon of agglomeration first demonstrated by Laveran 

 and Mesnil (1900a) in the case of Trypanosoma lewisi may be regarded as 

 throwing some light on this question. When acted upon by certain sera 

 the trypanosomes become clustered in rosettes, with their flagellar or 

 anterior ends directed outwards and their non-flagellar ends united at 

 the centre of the cluster (Fig. 152, A). Schindera (1922) has shown that 

 Cryptobia helicis of the snail similarly becomes agglomerated under the 

 influence of sera. In this case, again, it is the anterior end with the 

 free flagellum which is directed outwards, while the posterior end with 

 the posterior flagellum is at the centre (Fig. 152, B). 



