1912.] 



Ducks to T. gallinarum and T. gambiense. 



381 



more slender drawn-out individuals may occasionally be reversed in 

 direction. 



" As it is impossible to tell when the flies first received the infecting 

 trypanosomes, I have no information as to the exact sequence of forms in the 

 cycle. The main outlines are, nevertheless, pretty obvious, and the massive 

 broad forms gradually give place to smaller and more slender crithidial 

 individuals, some of which, in what appears to be the later flies, show a 

 considerable lengthening out of the body. 



" As will be seen from the drawings (Plate 9), true trypanosome-phases 

 have not been observed. Multiple division takes place, and is not by any 

 means a very rare occurrence, although here, as in most trypanosome-cycles 

 binary fission is the usual method of multiplication (see figs. 1, 2, 4, and 9). 

 The process in question is rather irregular, and, after carefully studying a 

 considerable number of these appearances, it becomes clear that it is a mere 

 telescoping of successive binary divisions. 



" The flagellate contains in the earlier infections a relatively large amount 

 of dense protoplasm, and we have thus an illustration of the common 

 biological process, whereby, in a cell encumbered with much protoplasm, 

 the nuclear apparatus may undergo several successive divisions before the 

 correlated splitting of the cell-body is accomplished. 



« Morphology. — The films were fixed wet, by dropping them face down- 

 wards on to Schaudinn's fluid. The stains used were iron-heematoxylin, after 

 Heidenhain's method, and haemalum. 



" The protoplasm, especially in the broader forms, is very dense and 

 granular, a feature which is somewhat less marked in the later stages, 

 Unfortunately, this density of the protoplasm obscures the final cytological 

 details to a greater or less extent. 



" The trophonucleus is of a common trypanosome type, consisting of a 

 large central karyosome surrounded by a clear space, which is bounded in 

 turn by a delicate membrane ; fine rays pass from the karyosome to the 

 membrane. 



" The kinetonucleus (centrosome of French and blepharoplast of German 

 writers) lies close to and generally in front of the trophonucleus. It is 

 relatively large, and presents the somewhat curious double appearance of 

 two closely-apposed granules lying one behind the other. This does not 

 seem to be in any way a case of precocious division. 



"In fig. 4, where division is actually in process, and where the two 

 kinetonuclei are still joined by the centrodesmose, they nevertheless 

 preserve the double appearance, and, in a case of multiple fission figured 

 (fig. 9), the same thing is to be observed. Moreover, the direction of the 



2 D 2 



