158 University of California Publications in Zoology [VOL. 19 



is the one shown in figure 12, plate 2. The anterior end of the body 

 is slightly shortened but the nuclear structure has the same general 

 appearance. Only one bud has been given off, and this lies directly 

 posterior to the nucleus proper. As in the former case, the chromatin 

 is collected on the inner surface of the nuclear membrane of both the 

 nucleus and endogenous bud. In figure 13, plate 2, a more complex 

 organization was observed. The nucleus and two clearly defined 

 nuclear buds are arranged in a linear series, the two buds being pos- 

 terior to the nucleus proper. Partially concealed by the nucleus is a 

 third bud, which is being constricted off from the nucleus. This par- 

 ticular view of the process is in all probability an end view and only 

 a portion of the bud is visible. If the observations and interpretation 

 of this structure be correct, the nucleus, with all of its chromatin col- 

 lected on the inner surface of the membrane, repeatedly constricts or 

 buds off a portion, forming a series of nuclear buds (pi. 2, figs. 13, 

 20, 21). There is at hand at present no evidence of a central karyo- 

 some being present in the nucleus when endogenous buds are formed. 

 The nuclear buds, therefore, in so far as our observations have gone, 

 are due neither to a clearly defined amitosis nor to a primitive form 

 of mitosis of the chromatin material which normally occurs in a 

 central karyosome. 



Although evidence of a mitotic process in this nuclear division is 

 wanting, nevertheless some evidence of a promitosis has been found in 

 the division of the nucleus in an early stage of the formation of a soma- 

 tella (pi. 3, fig. 25). The formation of the somatella involving the 

 " rounding up " of an elongate flagellate into a sphere will be described 

 shortly; it will suffice for our purpose here to point out salient fea- 

 tures of the internal structure of the ''rounding up" flagellate (pi. 3, 

 fig. 25). The blepharoplast, parabasal body, and the rhizoplast of this 

 flagellate have not yet begun to divide but the nucleus is beginning to 

 form two daughter-nuclei. The central karyosome which is normally 

 present in C. euryophthalmi has formed two unequal masses of chro- 

 matin connected by a centrodesmose. No critical evidence was found 

 showing that there is present at each end of the controdesmose a cent- 

 riole or centrosome differentiated from the chromatin material in this 

 minute form. Peripherally there is the nuclear membrane still present 

 and intact, but it is constricting in the center to form two nuclei. If a 

 similar division of the chromatin material occurs in the nuclear bud- 

 ding it has thus far escaped observation. The number of early stages 

 of nuclear budding studied has been small, owing to the rarity of 



