1920] SHARP— SPERMATOGENESIS 265 



A iurther objection may be seen in the case of animal sper- 

 matogenesis, in which an undoubted centrosome elongates with- 

 out fragmentation as it performs its role in the development of 

 the motor structures. It is noteworthy, however, that cilia are 

 frequently seen growing from recently divided centrosomes in the 



spermatocytes (Henneguy 



same 



blepharoplast granules in Equisetum (Sharp 8). Moreover, in the 

 Flagellata, which should furnish evidence more valuable than that 

 in the higher animals, it is known that in certain cases blepharo- 

 plasts arise from functional centrosomes by division (see Mix- 

 chin 7, pp. 82 ff.). 



Although there is thus seen to be considerable evidence for the 

 derivation of blepharoplast fragmentation from normal centrosome 

 division, this evidence is probably best regarded as scarcely suffi- 

 cient to warrant the establishment of such an interpretation as 

 a general theory. 



The question of the relation of the centrosome to the blepharo- 

 plast has been fully discussed by the writer in his papers on 

 Equisetum and Marsilia (8, 9). It will be sufficient here to recall 

 that the conclusions were reached that the blepharoplasts of bryo- 

 phytes, pteridophytes, and gymnosperms are " ontogenetically or 

 phylogenetically centrosomes " (Ikeno); that these centrosomes 

 become more and more restricted in the life history in passing 

 upward through these groups; that they are retained 

 matogenous cells because of the biological importance of the 



m 



which 



m 



profoundly modified 



many 



exhibited 



these 



confirms 



plasts arising from centrosomes functional in mitosis. How exten- 

 sive this centrosome behavior is in the case of Blasia the present 

 study may not show, for, as stated in the description, the writer's 

 material does not enable him to say whether the bodies in ques- 

 tion arise from Dreexistine ones bv division or not, or whether they 



