Glossina palpalis and Trypanosoma gambiense, etc. 243 



or more usually anterior to it. Sometimes, however, it may be posterior 

 to the nncleus, a point which we discuss further below. The flagellum 

 is often distinctly thickened at the tip. This type varies very greatly 

 both in form and size. We distinguish (1) male forms, very slender, 

 with long free flagellum, with nucleus very compressed, and with the 

 blepharoplast situated in front of it (Plate 13, figs. 21 and 22). Some 

 of the forms reach an extraordinary length (Plate 13, fig. 33). (2) Female 

 forms which are bulky, often thickened at the posterior end and with 

 an oval or rounded nucleus. The blepharoplast is variable in position, and 

 the free flagellum is very short (Plate 13, figs. 23 — 25 and 34). (3) Young 

 forms (Plate 13, figs. 31 and 32) and indifferent forms, varying greatly in 

 character ; among the latter we may particularly note forms which are nearly 

 spherical (Plate 14, figs. 43 — 51). The very protean character of these forms 

 (see Plate 13, figs. 35 — 40 ; Plate 14, figs. 41 — 52) makes it very uncertain as 

 to whether they are really all of the same species. Since, however, we have 

 noticed a marked difference between trypanosomes from flies which had fed 

 after being caught and those in flies which had not fed (Plate 13, figs. 33 

 and 34, and Plate 14, fig. 41), we think that these variations of type are to be 

 explained as the result of the conditions of nutrition of the host. The forms 

 from flies which had not been fed were both scarcer and larger than those 

 from flies which had recently sucked blood. In flies dissected soon after 

 feeding it was found that small forms (Plate 13, figs. 31 and 32) largely 

 predominated, and dividing forms were numerous (Plate 13, figs. 27, 28, 

 and 29) ; on the other hand, in those cases in which flies were found to 

 contain forms of a more indifferent character (Plate 13, figs. 36 — 40), it was 

 noticed that stages of division were extremely rare, and that aggregations 

 of similar forms into large masses were frequent (Plate 14, fig. 42). 



The mode of division in T. grayi is noteworthy and characteristic. The 

 two sister individuals which result from it are markedly unequal in size 

 and differ also in the relations of their nucleus and blepharoplast. The 

 smaller of the two has the blepharoplast placed in what may be considered 

 the normal position, that is to say, well in front of the nucleus. On the 

 other hand, the larger individual has the blepharoplast placed behind the 

 nucleus (Plate 13, fig. 28). We consider, therefore, that the forms not 

 infrequently found, in which the blepharoplast is situated behind the 

 nucleus, represent, in many cases at least, the larger of two sister 

 individuals resulting from recent division. Multiplication by division has 

 only been observed by us in individuals of indifferent or female type, never 

 in fully differentiated male forms. Finally, we may draw attention to the 

 numerous chromidia always present in young, indifferent, or female forms. 



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