igi2] SHARP— SPERMATOGENESIS IN EQUISETUM 107 



arrange themselves in a row and coalesce to form the cilia-bearing 

 band. 



nomena 



evident. Although limited to a single mitosis 



most 



centrosome 



metamorph 



In thus combin- 



main characteristics of true centrosomes 



features of the most advanced blepharoplasts, it reveals in its 

 ontogeny an outline of the phylogeny of the blepharoplast as it is 

 seen developing through bryophytes, pteridophytes, and gymno- 

 sperms, from a functional centrosome to a highly differentiated 

 cilia-bearing organ with very few centrosome resemblances. In 

 Marsilia the same pronounced centrosome behavior is shown 

 through at least three cell generations, and in the formation of the 



foreshadow 



marked 



To the present writer 



seem 



Iken 



has gradually assumed the function of bearing cilia, at the same time 

 losing the usual properties of a centrosome. 



The points brought out in such a review are especially suggestive 

 in connection with the conclusions to which Webber has been 

 drawn by his studies on Zamia (90). This investigator empha- 

 sizes very strongly the view that the blepharoplast is a distinct 



rmer 



centrosome nature. He Doints out that it differs from 



true 



the poles and having no connection with spindle formation, in 

 being limited to a single cell generation, in its great size, in its 

 fragmentation, in its growth into a band, in its function of bearing 

 cilia as far as plant centrosomes are concerned, and in its behavior 

 in fertilization. Although the blepharoplasts of other plant groups 



must 



formulated largely through a consideration of the cycad situation. 

 W hen the blepharoplast is regarded as an organ developing pro- 



gressiv 



gvmnosperms 



