STUDIES ON AVIAN H^MOPROTOZOA. 677 



parasites found in the autumn is of course greater, but the 

 difference is not relatively more than that between the larger 

 and the smaller fusiform individuals in the summer. A 

 difference which might appear of more importance is that in 

 the character of the cytoplasm in the two cases. This can 

 probably be explained, however, by supposing that the 

 cytological features shown by the large massive individuals 

 in the redpoll have become more developed and consequently 

 more prominent, as a result of the increase in size. And, on 

 the other hand, there is no evidence whatever that the 

 fusiform parasites will pass directly into the characteristic 

 ordinary type. 



Assuming, then, this connection between these two 

 sets of forms, how are we to explain the condition met 

 with in the winter and early spring, when the only type 

 of individual in the blood is the ordinary definitive form ? 

 The answer to this depends largely, I think, on what 

 significance is to be assigned to the large massive forms just 

 referred to. Ai-e they to be considered as sexual individuals 

 — of the female type ? This is, of course, possible, but more 

 than that cannot be said. And if this is the case, I certainly 

 do not know which are the individuals of male sex; there do 

 7iot appear to be any forms present at the same time which 

 could be so regarded. On the other hand, I think it is at 

 least quite as probable that the massive individuals have 

 grown to this size prior to multiplication ; they may later 

 undergo some process of multiple fission or segmentation, 

 occurring in one of the internal organs, and so give rise to 

 the small forms. This supposition would fit in very well with 

 the condition found, for instance, in case A (in the spring), 

 where, as we have seen, small parasites are numerous in the 

 bone-marrow, along with the ordinary forms, the latter being 

 probably to some extent replenished from them. And here 

 there are no signs of the large massive individuals. At all 

 events, in view of Chagas' recent important work (2), showing 

 that a new human trypanosome, Schizotry panum cruzi, 

 has a method of multiplication by multiple fission or 



