642 H. M. WOODCOCK. 



which the celeVjrated protozoologist, the late Fritz Schaudinn, 

 was led as the result of his well-known researches (27) 

 on certain parasites of the little owl (Athene noctua), have 

 been largely discredited by many subsequent workers in this 

 field. 'Jliis is chiefly due to the suggestion, first put forward 

 by the American workers, Novy and McNeal, that there is 

 nothing in Schaudinn's description to show thatthe author took 

 sufficient precaution against the liability of confusing the life- 

 histories of what wei'e really separate and independent para- 

 sites. Novy and McNeal, in theii- endeavour to confirm 

 Schaudinn's views, investigated the trypanosomes of various 

 birds (14), and also made a study of the flagellates occurring 

 naturally in mosquitoes (15). As a result of their work they 

 have maintained that Schaudinn was entirely wrong in regard 

 to all his main conclusions. They consider, on the contrary, 

 that the trypanosomes of birds are quite distinct from 

 intra-cellular parasites (such as Halteridium), and further, 

 that they do not undergo any part of their life-cycle in an 

 insectan host, the flagellates occurring in the latter having 

 no connection with the trypanosomes. 



I chose avian forms ot^ which to work for the following 

 reasons: In the first place, a considerable amount of research 

 has now been done on various trypanosomes parasitic in other 

 vertebrates, e.g., fishes and mammals, which will be referred 

 to in due course. Secondlv, it is from a studv of avian forms, 

 if any, that one may reasonably expect to learn how far 

 Schaudinn's views and statements were justified. As a 

 matter of fact, at the present time the trypanosomes of birds 

 are those about which the least is positively known, for 

 Novy and McNeal's work, while it has undoubtedly re- 

 opened the entire question, does not, on the other hand, 

 contribute much to its definite settlement. In my opinion, 

 many of the conclusions reached by these authors ai-e equally 

 open to criticism. They themselves have certainly not 

 l)rought forward adequate or sufficient evidence to justify 

 the negative views adopted by them. 



Hosts Selected to Work upon. — It was my intention 



