STUDIES ON AVIAN H^MOPROTOZOA. 671 



describing the parasites which occur in the iater case(B). 

 The smallest individuals have been found in the boue- 

 marrow. The trypanosomes are distinctly Jess frequent in 

 the bone-marrow than they are in the general circulation, 

 and the individuals which do occur in this situation are 

 nearly all small or minute in size. One of the smallest forms 

 seen is drawn in tig. 40. Its total length is 15 u, that of the 

 free flagellum alone being 4 ju ; hence the length of the body 

 itself is 11 ^. The width is a trifle under 2^ ju. It is only 

 necessary to compare this parasite with some of those above 

 described to realise the great difference in size which may 

 be shown by different individuals of the same species of 

 avian trypanosome. Another very small individual (fig. 5) 

 has a total length of 18 ju, partly accounted for by the 

 rather longer flagellum of 8 ju, and its greatest breadth 

 is 3 lu. 



On the other hand, the largest individuals belonging to 

 this series of forms which I have observed are seen in figs. 

 44 and 45. The parasites are of only medium size ; they do 

 not really come in the category of large forms. The trypano- 

 some of fig. 45 has a length of 33^^, its flagellum alone is 

 8^ fjL, and the greatest breadth is 5^ /n. The dimensions of the 

 other individual are rather less. Between these two extremes 

 of this type parasites of all intermediate sizes occur — 

 forming, indeed, a regular gradation. This is illustrated by 

 figs. 6, 42, and 43. The trypanosome in fig. 6, for 

 instance, is 23 /u in total length, of which the flagellum is 

 Q\ H, and has a width, including the undulating membrane, 

 of of ju ; again, the individual of fig. 43 is '11 fx long, the 

 flagellum alone 6/1, and the breadth 4A //. 



As will be noticed, tliere is a general similarity in form 

 between all these parasites. The body is fusiform or spindle- 

 shaped, and fairly wide in proportion to its length; it is 

 quite distinct in appearance from the body of a definitive 

 individual. The aflagellar end is drawn out and pointed, 

 but it is not so elongated and attenuated as in the case of the 

 definitive parasites described above. In the smallest indi- 



