224 



THE HAEMOFLAGELLATES 



dumb -bell -shaped, after which the two halves become farther 

 separated, remaining connected only by a short thread (B). 

 The chromatin of the trophonucleus is arranged in eight rather 

 elongated chromosomes, which next begin to divide in a similar 

 dumb-bell-like manner (Fig. 18, c). The trophonuclear karyosome 

 (karyocentrosome) has frequently divided by this time ; but in 

 one instance Prowazek observed it much drawn out and functioning 

 as an intranuclear division centre (n), the chromatin having 

 become aggregated around its ends. 



In her account of T. raiae in Pontobdella Miss Robertson (I.e.) 

 has gone at length into the question of nuclear division. The 

 kinetonucleus appears to divide by a simple kind of mitosis though 



FIG. 19. 



A-D, stages in the binary longitudinal tission of 7'. r</ inn m ; K, multiple fission in the same 

 parasite ; F and G, binary and multiple division in T. cfiuiperdum. (After Lignieres.) 



the details are extremely obscure. The trophonuclear division also 

 takes place by a simple kind of mitosis, but shows a well-defined 

 achromatic figure (comparable to a series of axial fibrils). This 

 probably arises from the trophonuclear centrosome. The figures 

 showing the later phases of the process convey quite the same idea 

 as does Fig. 12 of T. grayi. In fact, this case also appears to 

 conform to the same general plan as those above described. 



The division of the cytoplasm takes place last. In the great 

 majority of forms this is equal or sub-equal, and the two resulting 

 daughter-Trypanosomes are of approximately the same size (Figs. 

 17 ; 19, c). Although the cytoplasmic fission usually begins at the 

 flagellar end, it may start at the opposite extremity (cf. Fig. 19, D). 

 In some instances (Fig. 19, E and G) the longitudinal fission is 



