THE H/EMOFLAGELLATES. 150 



doubt that many autliors liave not taken this factor suffi- 

 ciently into account in coustnictiug what they regarded as 

 the normal life-histoi'y of the Trypanosome concerned, and 

 that much of the variety in form and mode of division wliich 

 lias been described is due to abnormal and altered appearances 

 of the parasite. These involution forms in reality represent 

 the commencing degeneration of the Trypanosome and are to 

 be carefully distinguished from its typical phases. 



Schaudinn's Work on the Life-cycle of a Try- 

 panosome. — The normal life-cycle of a Trypanosome can be 

 studied much more easily and, it may be said, only thoroughly 

 when it is undergone in the host or hosts to which it is by 

 nature specially adapted, and which, on their part, have 

 become accustomed to that particular parasite. It is highly 

 significant that when an investigation under these conditions 

 has been cnrefully undertaken, as recently by Schaudinn (98), 

 in the case of two common, well-tolerated Tr3-pnnosomcs of 

 the Little Owl, ^ a more complete and comprehensible account 

 of the whole life-history is made known as the result than 

 had, up till then, been given for all the Mammalian Trypano- 

 somes put together. Especially noteworthy is Schaudinn's 

 revelation of the part played by the " carrier" of these para- 

 sites — a gnat. Bruce was the first to demonstrate, in a bril- 

 liant manner, the carrying function of the Tse-tse fly^ in 

 Nagana or the Tse-tse fly disease, and he showed that this 

 Insect acts as the intermediary between wild game (tolerant 

 of the Nagana Trypanosome, and serving as a reservoir) on 

 the one hand, and domesticated animals on the other. 

 Following his methods, much has since been ascertained 

 by various workers concerning the bionomics of other species 

 — their probable source, mode of infection, carrying agents, 

 etc. Yet in no single instance had it been proved whether 

 the Invertebrate is a true alternate host, one, that is, in 

 which definite stages of the parasite's life-history are passed 

 through, until the publication of Schaudinn's work.'^ 



' Athene noctua. ^ Grlossina morsitans. 



' It is casting no reflection on this author's brilliant work to say that, 



