676 H. M. WOODCOCK. 



somewhat larger individuals of the fusiform type (figs. 49 

 and 51). The stumpy trypanosomes themselves ai-e best 

 regarded, I think, merely as division-forms of young to 

 medium-sized individuals of fusiform type. Hence, in this 

 case, it may be said that the fusiform parasites present are 

 of small to medium size and tend to multiply, by passing 

 into the stumpy division form, rather than grow, at any 

 rate at this period, into large trypauosomes. Next, with 

 regard to the very thin, slender forms (e.g. figs. .5.5 and .56) : 

 when first seen they appeared in such sharp contrast to the 

 prevailing stout type of parasite that I was somewhat dis- 

 posed to think they represented male forms. As above 

 mentioned, however, I am now more inclined to look upon 

 them as young definitive parasites, which would grow into 

 medium-sized ones, such as those in figs. 4 and 31, and so 

 to full-grown adults, as in figs. 2, 28 (all from this series). 



Turning again to case B (the later case), we find no 

 ordinary forms present. Fusiform individuals of medium 

 size are not uncommon, and between these and very small 

 forms parasites of all intermediate sizes occur. There are 

 very few stumpy forms, and none of those found show any 

 actual signs of division.^ Hence, the main condition here is 

 undoubtedly a series of steadily growing fusiform individuals. 



There remain two or three interesting questions in con- 

 nection with the different type or phase of the infection 

 occurring at different periods, in regard to which I can only 

 put forward those surmises which seem to me the most 

 probable. In the first place, comparing the condition found 

 in a chaffinch (case B), in the summer, with that obtaining in 

 a redpoll in the early autumn, where the parasites are mostly 

 of the large massive type (e.g. figs. o4-.36), I think it is 

 most likely that the fusiform parasites of the former case 

 (such as those of figs. 44, 45), would grow ultimately into 

 individuals corresponding to those of the latter. The body- 

 form is essentially similar in the two cases. The size of the 



1 It is possible, however, that the two or three small stumpy indi- 

 viduals seen in this case may be about to divide. 



