148 University of California Publications in Zoology [Vol. 19 



ment of slightly greater staining intensity can be observed at the 

 junction of the parabasal rhizoplast with the nuclear rhizoplast. In 

 C. euryophthalmi (fig. A, 2) even greater difficulty is experienced in 

 endeavoring to find the blepharoplast. In this form there is no en- 

 largement of the base of the fllagellum, but the area at the junction of 

 the rhizoplast is darker in appearance, and frequently a small granule 

 at one side can be seen by careful focusing. 



Among the trypanosomes the blepharoplast is apparently a more 

 clearly defined structure. Our investigations of T. triatomae (fig. 

 A, 4) have yielded more tangible results. We found in this trypano- 

 some a slight enlargement of the base of the flagellum but no differ- 

 entiation in the staining capacity of the flagellum and basal granule. 

 In T. Icwisi (fig. A, 3) and in Schizotrypanum cruzi (fig. A, 5) the 

 figures of these trypanosomes show what is evidently a well defined 

 basal granule, or blepharoplast. This is particularly true of T. lewisi 

 (fig. A, 3). In both the crithidias and the trypanosomes the blephar- 

 oplast frequently divides independently of the nucleus. In the binary 

 fission of C. euryophthalmi the blepharoplast and parabasal body 

 may divide before the nucleus divides (pi. 3, fig. 4), or the nucleus may 

 divide first (pi. 3, fig. 33). In figure 25, plate 3, the nucleus is divid- 

 ing but there are no indications of the division of blepharoplast and of 

 the parabasal body. A similar condition exists among the trypano- 

 somes, indicating that the blepharoplast is the kinetic center of the 

 extranuclear organelles, or neuromotor apparatus. But this is not 

 the only kinetic center of these simple organisms. The nucleus also 

 contains a kinetic center which initiates division in the form of a 

 centrosome, at the base of the nuclear rhizoplast in those flagellates 

 containing this organelle. In the nucleus of S. cruzi (fig. A, 5) this 

 centriole, or centrosome, at the base of the nuclear rhizoplast is clearly 

 defined within the central karyosome of the nucleus. The origin of 

 the blepharoplast is still the subject of investigation and as yet no 

 conclusive evidence is at hand to establish beyond doubt the way in 

 which this structure originates. In the endogenous buds, which are 

 exceedingly small and difficult to interpret, the blepharoplast seem- 

 ingly originates from the single nuclear structure as an outgrowth 

 rather than by a mitotic process. The outgrowth forms a second 

 deep-staining mass anterior to the nucleus, and at this stage the 

 nonflagellated forms have the appearance of "binucleated" spores. 

 As development proceeds the kinetic center of the blepharoplast is 

 probably established as the center of the neuromotor apparatus, and 



