132 University of California PnhUc-ations in Zoology [Vol.20 



homologous with those of a like structure in Giardia, where this 

 granule plaj'S the role of the centrosome at mitosis. This centrosome 

 is seen with difficulty, if at all, owing to its juxtaposition to the large 

 chromatin plaque and sometimes to the position of the nucleus which 

 may be so turned as to obscure it. At mitosis in Chiloniastix this 

 granule divides and the daughter centrosomes form the paradesmose 

 between them as a fiber on the nuclear membrane (pi. 16, fig. 15). 



A comparison of the position, structure, and relations of the 

 blepharoplasts in the free flagellate with those of the encysted stage 

 indicates that the nucleus in its postero-lateral migration to near the 

 center of the cytoplasmic mass has not only drawn out the long rhizo- 

 plast from the left blepharoplast but has also parted the lilepharopla.sts 

 more or less widelj^ (pi. 16, figs. 8, 11). 



In the encysted stage the primary blepharoplast (fig. B, prim, 

 blcph.), has lost its two anterior flagella, is often quite small, dis- 

 located laterall.v to the left and connected by the nuclear rhizoplast 

 {nuc. rhiz.) to the centrosome {cent.) on the anterior face of the 

 nucleus. The transverse rhizoplast {tr. rhiz.) joins it to the secondary 

 blepharoplast (sec. bleph.) which has lost its single right flagellum. 

 This granule and the preceding are often about equal in size to 

 the primary blepharoplast. The tertiary blepharoplast lies near the 

 ventral surface at the anterior end of the cytostome, receives the peri- 

 stomal rhizoplast, and gives rise posteriori}' to three structures: (1) 

 to the cytostomal flagellum which, unlike the free flagella, persists as 

 a deeply staining fiber during the early phases of the cyst, (2) to the 

 curved parabasal, a deeply staining rod in the right wall of the oral 

 pouch, and (3) to the peristomal fiber in the margin of the opening 

 into the cytostome. The latter is so delicate and so superficial in 

 location as to require great care in differentiating it from the under- 

 lying parastyle and parabasal. 



The unity, fibrillar continuity, and elasticity of the neuromotor 

 system is again demonstrated in the structure and behavior of the 

 centroblepharoplast complex of Chilamastix during encystment. 

 Though divided into centrosome and three blepharoplasts the fibrillar 

 continuity of the complex is maintained unbroken in encystment and 

 mitosis. 



The cj'tostomal complex is clearly recognizable in the cyst, both 

 in the iodine-eosin stain and in the iron haematoxylin, as an elongated 

 or slipper-shaped loop with a contracted region anteriorly. A dark 

 thread, the peristomal fiber, outlines the opening into the shallow 



