1920] Kofoid-Swczy: Morpholof/y and Mitosis of Chilomastix 137 



SUMMARY 



1. Chilomastix m.csnili lias a deep spiral groove running posteriorly 

 from right over to left as a permanent cell organ distinct from but 

 adjacent to the eytostome. It persists in the cyst as a meridional 

 structure. 



2. The neuromotor apparatus consists of centrosome, nuclear rliizo- 

 plast, three blepharoplasts and connecting rhizoplasts, the primary 

 giving rise to two flagella, the secondary to one and to the parastylc, 

 the tertiary to the parabasal, the peristomal tibril, and the cytostomal 

 flagellum or undulating membrane. 



3. The centroblepharoplast complex is thus subdivided into four 

 granules, the centrosome and three blepharoplasts having continuous 

 rhizoplast connections with the central karyosome of the nucleus. 



4. The nucleus is polarized with the centrosome anterior and the 

 spireme forms in its longitudinal axis. Binary fission in the cyst is 

 morphologically longitudinal. 



5. The blepharoplast-rhizoplast chain splits lengthwise at mitosis 

 . and the remainder of the neuromotor complex appeal's to be produced 



de novo by outgrowths from the blepharoplasts prior to the spireme 

 stage. The daughter centrosomes are connected by a paradesmose. 



6. In mitosis the nuclear membrane remains intact and its con- 

 struc-tion is spatially transvei-se. The daughter nuclei are for a time 

 connected by the paradesmose but lie at opposite poles of the cyst, but 

 may later change their position. 



7. The neuromotor system of Chilomastix is strikingly similar to 

 that of the right half of Giardiu in symmetry and its constituent 

 elements. 



8. The two daughter individuals have the same symmetry; they 

 are each equivalent to the right half of Giardia. 



9. The bilateral symmetry of the two-celled Giardia could arise 

 only by a complete morphological reversal from the sinistral to the 

 dextral type of one of the two daughter schizonts at mitosis. 



10. The genus Chilomastix is closely related in structure to and 

 may be the source of the bilateral binucleate Hexamitidae. 



Transmitted March 30, 1920. 

 Zoological Laboratory, 



Vniversity of California, 

 BerTceley, California, 



