228 J. MCA. KATER. 



The poles of the spindle are lodged in centrioles which are located 

 on the outside of the nuclear membrane. An indication of 

 rhizoplasts connecting the basal granules with the nucleus have 

 been seen in both resting and dividing cells. In the early cysts 

 no basal granules can be seen. Before excystment a centriole and 

 new basal granules arise from the karyosome. This material is 

 drawn out of the latter body without disfiguring it. There is, at 

 first, a single basal granule which divides before reaching the 

 periphery. A rhizoplast is very evident during this phase. The 

 new flagella grow out after the organism is partly excysted. The 

 questions not answered are: is a centriole present in the resting 

 cell of the active form ; what becomes of the rhizoplasts that are 

 so evident before excystment ; are the basal granules drawn into 

 the karyosome at the beginning of encystment or do they 

 degenerate? 



In view of the fact that a centriole can be seen in division 

 stages, is very pronounced in the cysts and that Doflein has 

 demonstrated an extra-nuclear centriole in Polytomella agilis I 

 think we can conclude that such a center is present in the inter- 

 kinetic cell of P. citri. In addition the paradesmose, which is 

 quite evident, would, presumably, come from a centriole. Jame- 

 son (1914) says that Parapolytoma has no centriole. He mentions 

 Chilomonas and Polytoma as other examples of flagellates without 

 this division center. It is to be noted that Belar (1916) demon- 

 strated a centriole in Chilomonas and Entz (1918) showed that 

 Polytoma has a very definite one on the inside of the nuclear 

 membrane, with a heavy centrodesmose appearing at division. 



Aragao figures rhizoplasts connecting the basal granules of P. 

 agilis with the nucleus. Hamburger did likewise for Dunaliella. 

 In view of these observations, coupled with what has been seen in 

 P. citri I believe we are justified in assuming that the rhizoplasts 

 are constant structures in P. citri. 



Berliner states that the basal granules of Copromonas are drawn 

 into the endosome at division. His figures, however, are not at 

 all complete. Jameson finds that the basal granules of Para- 

 polytoma never divide, but three of the four individuals resulting 

 from division receive new basal granules from the karyosome. 

 Entz finds that the centriole and blepharoplasts of Polytoma arise 



