96 



1STR0DVCTI0N TO CYTOLOGY 



Although there is comparatively little question that the granule at the 

 base of the flagellum in the flagellates, like the body from which the axial 

 filament of the spermatozoon grows, is of centrosomic nature, the nature 

 of the basal granules in Ciliata and in the ciliated epithelial cells of higher 

 animals is much more difficult to determine. It was held by Henneguy 

 (1897), Lenhossek (1898), Hertwig (1902), and others that these granules, 

 like the basal granules of flagella, are modified centrosomes; whereas 

 certain other investigators (Maier 1903, Studnicka 1899, Schuberg 1905) 

 have found evidence in favor of a contrary interpretation. An extensive 



l- .... /, A \ 



k\nM\ 



W* 



Fig. 35. — Spermatogenesis in Helix pomatia, 

 showing growth of flagellum from outer centro- 

 some, and elongation of inner centrosome to 

 form axial filament of middle piece. (After 

 Korff, 1899.) 



Fig. 3(3. — Diagram of a ciliated epi- 

 thelial cell. (Constructed from figures of 

 Saguchi, 1917.) 



discussion of this question is given by Erhard (1911), who concludes that 

 although the basal corpuscles arise from the nucleus in a manner similar 

 to that of the centrosomes of such cells, the evidence is on the whole 

 unfavorable to the theory of Henneguy and Lenhossek. 



Still more recent are the researches of Saguchi (1917), who describes 

 in great detail the insertion of the cilia in epithelial cells. At the base 

 of each cilium, which itself shows no internal structural differentiation, 

 there is always a basal corpuscle (Fig. 36). These corpuscles, and hence 

 the cilia, are in parallel rows; and beneath each row there is a transparent 

 zone in which the rootlets of the cilia are anchored, and through which 

 they pass and become continuous with strands of the cytoplasmic recti- 

 culum. Cilium, corpuscle, rootlet, and cytoplasmic strand form one 

 continuous structure. Saguchi believes that neither the cilium nor the 

 rootlet causes the ciliary movement, but that the kinetic center of this 

 movement is in the basal corpuscles, as Henneguy and Lenhossek thought. 

 Contrary to the opinion of those authors, however, he regards the ciliary 



