1 9 1 2] YA MA NO UCHI—C U TLERIA 477 



stance of the nucleolus is utilized for spindle formation, the conclu- 

 sion being drawn from the fact that the nucleolus disappears partly 

 or completely immediately preceding the formation of the spindle. 

 Williams (66) in his study of Dictyota accepted this view. Stras- 



burger 



servm 



(61) on Stypocaulon and by Mottier 



on Dictyota. The view that the chromosomes are formed directly 

 from the nucleolus was supported by Tangl (62) , Meunier (29) , 



Moll (30), Decagny (10), Henneguy (19), Van Wisselingh 

 (67-69), Berghs (3), Karsten (22), and Trondle (64) in their 

 studies of Spirogyra, by Wolfe (70) on Nemalion, by Lewis (27) on 

 Griffithsia, and by Svedelius (60) on Delesseria. These investiga- 



differ 



some 



xpressed 



contradictory 



quently the figures would afford better support to some 



interpretation. 



seem 



chromosomes 



from the material of the nuck , 



be used up partly or even entirely. 



A fourth opinion is that the chromosomes arise exclusively 

 from the chromatin network, the nucleolus taking no direct part 

 in their development. Fucus illustrates the situation. The 



Strasburger 



Farmer and Williams 



been furnished by the present author (73). Polysi- 



phonia (Yamanouchi 71), Corallina (Davis 



76) 



Cutleria and Aglaozonia, present a similar situation. 



THE ORIGIN OF BIVALENT CHROMOSOMES 



Contrasted with the formation of univalent chromosomes in 

 typical mitosis, the origin of bivalent chromosomes is rather com- 

 plex. As already described, in the resting nucleus of the zoospore 

 mother cell of Aglaozonia the chromatin network is composed of 

 granules and fibrils. While in tvDical mitosis the network finally 



