26 MORPHOLOGY AND CULTURE OF MICROORGANISMS 



grain. The centriole is united to the blepharoplast by a centrodesmose, 

 the rhizoplast, which is often absorbed. Finally, the last centriole 

 situated beyond the blepharoplast about equally distant, also unites 

 with this cell-organ by a centrodesmose and, by approaching the 

 extremity of the cell, causes the elongation of the centrodesmose which 

 transforms itself into a flagellum. 



In the infusoria the vibratile cilia insert themselves in the ectoplasm 

 and pass through the cuticle to reach the exterior. At the point of 



L ^'iBBI ;<end 



FIG. 16. FIG. 17. 



FIG. 1 6. A, Spongomonas uvella. The nucleus is undergoing mi to tic division. 

 Two centrioles, each at the base of a flagellum, are located at the two extremes of 

 the spindle. (After Hartmann and Chagas.) 



B, M.onas termo. The cell lies in repose; a centriole (a) lies at the base of the 

 flagellum; in (C) there are two centrioles, in (D) the two centrioles occupy the two 

 poles of the nucleus during the process of mitosis; in () exists the final nuclear 

 division. (After Martin.) 



FIG. 17. Fragments of the peripheral portion of Prorodon Ieres (infusorian) 

 with vibratile cilia and their basal corpuscles, (ect) Ectoplasm; (end) endoplasm; 

 (tr) trichocysts. (After Maier and Gurwitch.) 



insertion of each of these cilia is a small chromatic corpuscle or basal 

 grain, a trichocyst, also supposed to arise from a repeated division of 

 the centriole (Fig. 17). 



The centriole which, as we shall see later, seems to be a motor 

 organ associated with the internal cytoplasmic movements during 

 cellular division, appears also to be connected with the external move- 

 ment of the cell. 



