232 University of California Publications in Zoology [VOL. 19 



The plane of division runs parallel to the major axis and the 

 sulcus or chief longitudinal groove. The daughter blepharoplasts 

 separate and move to either side of this plane. The basal granules 

 divide earlier in the prophase, as do probably also each of the two 

 flagella, thus producing for each daughter blepharoplast two basal 

 granules and four flagella. I find no stages in which there are 

 shorter or unequal flagella, indicating outgrowth of new flagella, and 

 yet no evidence of splitting has been observed. 



The major sulcus deepens and in this plane there is a complete 

 peripheral cytoplasmic constriction (pi. 13, figs. 57-60). The cyto- 

 plasm rounds itself up and the daughter organisms are then held 

 together by a thin, highly vacuolated, protoplasmic connection, con- 

 taining one or more large vacuoles. Division is finally accomplished 

 by the rupturing of these vacuoles. At the time of final separation, 

 the chromatin masses are scattered irregularly through a clouded 

 nucleus. Part of these mass together, round up into a karyosome on 

 which is deposited the immediately surrounding cloud, thus leaving 

 a hyaline area. A large part of the chromatin remains on the out- 

 side of this hyaline area and tends to dissassociate, forming the 

 peripheral granular area (pi. 13, fig. 59). There is great metabolic 

 activity at this stage, for the whole cell, especially the anterior end, 

 is darkened by a chromidial cloud. At completion of nuclear re- 

 organization the rhizoplasts assume their small, almost invisible 

 appearance and the typical vegetative organism results. 



SUMMARY OF OBSERVATIONS 



1. Verification of the work of Carter (1865), Stein (1878), and 

 France (1899). 



2. Failure to find a contracting vacuole, a point upon which pre- 

 vious observers are at variance. 



3. Determination of a fundamental polarity and a superficial 

 symmetry, with anterior and posterior, sulcal and absulcal areas. 



4. There is evidence of a very primitive cytostome just at the base 

 of the flagella. The sulcus itself may be regarded as an extension 

 of the cytostome. 



5. The blepharoplast consists of two basal granules surrounded 

 by a granular archoplasm. When not sufficiently destained, it 

 resembles a more or less branched and attenuated mass, from which 



