﻿90 Proceedings of the Royal Physical Society. 



explaDation of the phenomenon. It does not appear to be 

 due to a refraction effect (Fig. 12, etc.). 



Before leaving the kinetonucleus, there is another cell 

 structure connected with it to be considered, although it is 

 only very rarely visible in the rounded-off state. This is a 

 very minute granule (Figs. 9 and 54) which seems to come 

 out of the kinetonucleus, and to be bound to it by a very 

 delicate thread. It usually, in the trypanosome and the 

 intermediate flagellate stage, lies posterior to the kineto- 

 nucleus, often at the extreme posterior tip of the body. It is 

 a very delicate and illusive structure, and difficult to see even 

 when present; it is, however, quite a definite cell element, 

 and divides at division of the individual, as can be seen in 

 Fig. 54. This little basal granule has, possibly, to do with 

 the anchoring of the kinetonucleus. Similar granules have 

 been described in H. muscce domesticm and also in many 

 trypanosomes. 



The phenomenon of chromidium formation is found at 

 times in these rounded-off forms, but as the significance of 

 the process is still obscure, I do not propose to go into the 

 question at the present time. It may be noted that indi- 

 viduals with chromidial nuclei are to be found in small 

 numbers at all stages of development (Fig. 7). 



Division. — Division occurs pretty freely among the rounded- 

 off forms, a circumstance which is indicated by the number 

 of individuals which present two nuclei and two kinetonuclei. 

 But it will be better to consider this process as a whole 

 later, after the different forms have been described. 



The nuclear features mentioned in the foregoing account 

 as occurring in the rounded-off forms are, as will be seen 

 from the figures, found in all the stages of development. The 

 modification which is seen in the trophonucleus of the long 

 slender type of trypanosome will be noted when this form 

 is described (Fig. 25). 



Among the rounded-off individuals just about the time 

 when the flagellar apparatus begins to develop, there are 

 found some very large forms, usually oval or pear-shaped. 

 They have a very considerable amount of protoplasm, and 

 the nucleus, which is usually large and rather irregular, 



