1.'i2 Univt rsity of California Publications in Zoology. IT° L - c 



tinguish any chromosomes, but the arrangement of the chromatin 

 in the form of an equatorial plate clearly supports the view thai 

 it is to be regarded as a form of mitosis. The end-bead together 

 with the fiagellum appears to take no part in this process of 

 division. Imt after the separation of the two daughter nuclei the 

 one closer to the trophonucleus seems to throw off a round body 

 from which a new fiagellum develops parallel to the old one. 

 Alter the division of the kinetonucleus is complete the tropho- 

 nucleus commences to divide. The intranuclear centrosome 

 becomes drawn out into a dumb-bell shaped form and the two 

 halves move apart until they lie one at each pole of the nucleus, 

 still remaining connected, however, by a fine line (PL 15, fig. 4). 

 The chromatin contained in the surrounding vesicle then .pre- 

 cipitates out iii the form of an equatorial plate, lying trans- 

 versely with regard to the two centrosomes (fig. 4). This stage 

 ill' division has been observed only mi very few occasions and so 

 must be passed through very rapidly. The equatorial plate then 

 splits transversely and each half moves up towards its respective 

 centrosome (fig. 5), finally collecting around il (fig. 6). The 

 connecting line between the two cent rosiinies eventually dis- 

 appears and each daughter nucleus gradually assumes the usual 

 form (tig. 7). In what manner the chromatin reconstructs the 

 clear oval vesicle around the intranuclear controsome is not quite 

 clear. .Meanwhile the second fiagellum has been elongating and 

 by the time the trophonucleus has divided is almost as long as 

 the original one (fig. 7). 



The animal then splits longitudinally, the fission commencing 

 at the anterior end and extending down until the two halves are 

 connected merely by their posterior extremities, in which position 

 they may remain for some little time before finally separating 

 (PI. 15, fig. 8). 



At certain stages of development this type of trypanosome 

 proceeds to the formation of cysts, or latent bodies. The pos- 

 terior extremity of the parasite swells up (fig. 14) and the pro- 

 toplasm, together with the trophonucleus, concentrates towards 

 this end (figs. 15-16), finally resulting in the formation of a 

 round or oval mass of protoplasm containing both nuclei and 

 provided with a lone- flagellum (fig. 17). This is eventually 



