STUDIES ON AVIAN H^MOPROTOZOA. 661 



This bird was then left alone for some weeks/ until with 

 the approach of summer I decided to look at it again and 

 see if the oncoming season appeared to make any difference 

 in the number or condition of the parasites. Examining a 

 cover-slip preparation on the afternoon of June IGth I was 

 surprised to see numerous microgametocytes of Halteri- 

 dium. The stimulus of cooling was causing many of them 

 to rupture the red blood-corpuscles, and rapidly form and 

 liberate the active male gametes. I had never seen any 

 Halteridia in the preparations or smears made previously 

 from this chaffinch; if this parasite was present then it must 

 have been extremely scarce in the peripheral circulation. 



I was so occupied with watching this process of the libera- 

 tion of the gametes and in endeavouring to see actual 

 conjugation stages (unfortunately without success) that I did 

 not search these fresh preparations for trypanosomes. In 

 permanent smears made at the same time, however, trypano- 

 somes occur, but they are not numerous (half a dozen or so 

 on a slide). 



Having this abundant Halteridium-material, and know- 

 ing the bird to be infected with trypanosomes also, I 

 determined to examine it in the night-time to see if I could 

 obtain any phases connecting these two types of parasite. 

 Blood taken at 1.30 a.m. on June 18th showed the same 

 condition as regards the Halteridia, and, in addition, Trypano- 

 somes were easily found, three and four respectively being- 

 seen in two cover-slip preparations without any difficulty ; 

 and there were probably several more in each. The trypano- 

 somes seen were manifestly much larger than the Haltei'idia, 

 and I saw no indications of a rapid transformation of the 

 Halteridia into trypanosomes, or vice- versa; indeed, the 

 only Halteridia observed free in these living preparations 

 were the adult gametocytes, male or female, behaving in the 



' The l)ird was not made use of during this period because I had now 

 given up making permanent preparations when a living drop failed to 

 show the parasites. I had learnt that the probal^ility was so much 

 against my finding any trypanosomes in a reasonable time. 



