1919] McCulioch: Life Cycle of Crithidia unci Trypanosoma 149 



from this blepharoplast the flagellum grows anteriorly and the para- 

 basal body to one side. Connecting the parabasal body with the 

 centrosome, or blepharoplast, is the parabasal rhizoplast (pb. rh.). 

 Parallel eases indicating such an origin of the blepharoplast can be 

 found among other flagellates. 



Parabasal body and rhizoplasts. — In all of these flagellates the 

 parabasal body (pb.) presents the same general appearance with 

 respect to its location, size and shape. In C. leptocoridis (fig. A, 1) 

 the parabasal body is a bar-shaped structure made up of two deeply 

 stained granules lying in close proximity. Immediately surrounding 

 this deep-staining bar is a clear area, limited by a sacklike covering 

 of dense cytoplasm, evidently continuous with the contractile cyto- 

 plasmic sheath of the flagellum. Between the parabasal body and the 

 blepharoplast region the cytoplasmic sheath takes on the appearance 

 of a cone-shaped mass of contractile fibers (pb. rh.), the apex of 

 which is found at the base of the flagellum and continuous with the 

 outer contractile cytoplasm of the flagellum. The axial or central 

 part of this parabasal rhizoplast is presumably of blepharoplastic 

 origin and connects the blepharoplast and parabasal body. 



The parabasal body of C. euryophthalmi is similar to that of 

 C. leptocoridis. It is not so large comparatively (fig. A, 2) and it 

 seldom has the bilobed appearance. In C. euryophthalmi the most 

 interesting and valuable evidence has been found concerning the 

 relation of the parabasal body to the blepharoplast. In text figure 

 B, 1-5 a series of flagellates has been drawn from good iron-haema- 

 toxylin preparations to show clearly that the position of the organelle 

 is lateral and not axial. In figure B, 1 the end of the bar-shaped 

 parabasal body, which lies lateral to the nuclear rhizoplast, extends 

 outward to the periplast. From another angle the entire length of 

 this organelle is visible (fig. B, 2) peripheral to the nuclear rhizoplast, 

 which passes behind and underneath the parabasal rhizoplast. Still 

 another aspect of the possible position of this structure is indicated 

 in figures B, 3, 4. In each of these figures it is medial to the nuclear 

 rhizoplast and behind or beneath it as it passes from the centro- 

 some of the nucleus to the centrosome, or blepharoplast, at the base of 

 the flagellum. In such a figure as B, 5 the relationship of this organ- 

 elle to the others of the neuromotor apparatus can be seen most clearly. 

 The cytoplasm has become exceedingly clear and does not conceal the 

 other structure. The parabasal body in the flagellate stains very 

 deeply and has the appearance of a chromotoidal mass suspended in 



