igi 2 ] YAMANOUCHI—CUTLERIA 481 



radiations, always only at metaphase, and as a rule completely 

 disappearing at telophase. It may be found that polarity does 

 not depend in all cases upon the presence of permanent protoplasmic 

 structures of recognizable size or upon such morphological differ- 

 entiation as to rank as organs of the cell. There may possibly be 

 polarity at times without visible protoplasmic organization, but 

 so far as the visible organization of the cell is concerned, there seems 

 to be no permanent polar organization in the cells of Cutleria and 

 Aglaozonia. The transient polar organization is formed de novo 

 at each mitosis in every possible position about the nucleus. The 

 variability of the polar axis of the mitotic figure demonstrates 

 the feature (fig. 13). 



Zoospores and gametes of algae invariably present a conspicu- 

 ous polarity in that their cilia are situated at one end or at a definite 

 point on the side, the point of insertion being devoid of plastids. 

 The most vital problem of zoospore and gamete formation is whether 

 the polar organization of these cells arises de novo at the time of 

 development or is handed down from the succession of the cells that 

 are their progenitors. Strasburger (57), from his studies of the 

 zoospores of Oedogonium, Cladophora, and Vaucheria, decided 

 that the cilia bearing organ, the blepharoplast, arises in the 

 plasma membrane (Hautschicht), the nucleus lying in close associa- 

 tion at the time of its formation. Mother (33) later described a 

 similar origin of the blepharoplast in Chara. Davis' work on 

 Derbesia (9) showed that the blepharoplast is developed at the 

 plasma membrane in the form of a ring that has been organized 

 by the side by side union of numerous granules arranged in a circle. 

 The marked polarity is manifested after the appearance of the 

 granules. 



The details of the organization of zoospores and gametes of 

 Cutleria and Aglaozonia have not been given in this account because 

 the subject will be dealt with in a special paper treating of the ori- 

 gin of motile sperms or spores of algae, such as Fucus , Zanardinia, 

 Ectocarpus, and of some green algae, so that -a brief account will 

 be sufficient for the present consideration of polarity. 



In the zoospore mother cell stage, which is usually reached at 

 the 8-nucleate stage of the zoosporangium, cleavage furrows start 



