STUDIES ON AVIAN H.EMOPROTOZOA. 657 



of the trypanosomes in the blood, I was uot able to make 

 use of the iron-hasmatoxylin method of staining. For there 

 is one distinct drawback to the Romanowsky method and 

 its variations. While it may be regarded as giving, after 

 fixation with osmic, a perfectly reliable presentation of the 

 form and general structure of the body, it is now quite clear 

 from the most recent research (see, for example, Minchin 

 [12] and Minchin and Woodcock [13]) that the nuclear struc- 

 ture and details cannot be interpreted correctly by the aid 

 of stains of this kind alone. This is owing to the invari- 

 able tendency of Romanowsky stains to deposit the red 

 colour in excess around certain orgauellfe, especially small 

 granules, which are thus overloaded with stain and arti- 

 ficially enlarged to many times their real size, often with 

 the result that other cytological features are quite obscured. 

 Nevertheless, this characteristic behaviour of the 

 Romanowsky stains being now proved and recognised, due 

 allowance can be made therefor, and hence one is not 

 likely to be seriously misled in the case of a study such as 

 is here described, which deals chiefly with the compara- 

 tive morphology and behaviour of different types of form. 

 Further, it may be pointed out that results obtained by the 

 use of the same methods throughout may be compared with 

 confidence. 



3. The Parasites in Relation to Their Hosts. 



Numerical Scantiness of the Trypanosomes. — Asa 

 rule, the trypanosomes are extremely scarce in the peripheral 

 circulation of an infected host. This fact renders it often 

 an excessively slow and wearisome process to get hold of the 

 parasites at all in a living bird, and hampers any work 

 upon them more than can be imagined until such research 

 has been attempted. Unfortunately, there is all but 

 unanimous agreement among observers upon this point,^ 



' The only exception of which I am aware is indicated by a statement 

 of Vassal (36) in describing a trypanosome from an Annam pheasant. 



