No. 500] NOTES AND LITERATURE 



547 



claimed that the blepharoplasts did not occupy the poles of the 

 spindle in the final mitosis, as would he expected of a centrosome- 

 like body. 



These divergent views have ureal theoretical interest in rela- 

 tion to the subject of the polar organization of cells reviewed in 

 the July number of the Naturalist. Zoospores invariably 

 present a conspicuous polarity since their cilia are situated at 

 one end or at a definite point on the side, and while the complex 

 coiled structure of many sperms obscures this polar organiza- 

 tion the process of blepharoplast development is always from a 

 region which is clearly a pole of the cell. Indeed, these types 

 of cells present some of the best illustrations of complex polar 

 organization. Perhaps the most vital problem of zoospore 

 formation and spermatogenesis is then the question whether or 

 not the polar organization of these cells arises de novo at the 

 time of their development or is handed on from the succession 

 of cells which are their progenitors. 



Davis 1 found in the zoospores of Derbesia a very interesting 

 subject for the. study of a remarkaUc hlephamplast. Derbesia 

 is a marine green alga in the group of the Siphonales, distin- 

 guished from other forms in the same group by having very 

 large zoospores, each of which is provided with a circle of 

 numerous cilia. These zoospores are developed in a large spo- 

 rangium which contains at first several thousand nuclei, but a 

 process of nuclear differentiation begins very shortly in the 

 young sporangium: certain of the nuclei increase in size while 

 the great majority begin to degenerate and finally break down. 

 The large surviving nuclei heeome distributed rather uniformly 

 throughout the protoplasm of the sporangium, and each is evi- 

 dently the center of dynamic activity for the cytoplasm in its 



