﻿i 9 i6] MERRI MAN— NUCLEAR DIVISION 323 



thinning in the center, while parts reassemble at either pole. The 

 chromatic bodies in the fixed disks appear as viscous masses that, 

 as they amalgamate, elongate, while other disconnected chromatic 

 masses are discharged into the cytoplasm as the disk separates 

 into the halves passing to the poles. 



The living disks may be seen sometimes to pass en masse to 

 the poles, but more usually they divide their substance into a 

 few continuous strands, to reassemble as disks at the poles of the 

 anaphase. These strands cannot be identified as moving chromo- 

 somes, since no units can be discerned in them. As the disks 

 approach the poles, they appear to blend with similar disks 

 apparently evolved from cytoplasm. 



Each daughter disk thus arising upon fixation consists of a 

 series of about 4 rows of tetrahedral masses. In living material 

 the same appears as a translucent rim surrounding a less dense 

 interior. The translucent rim becomes the nuclear plasm, while 

 the central body takes shape within the less dense interior. 



Spirogyra, as exemplified in 5. bellis and S. crassa, may be 

 characterized as having chromatic substance of a polymorphous 

 nature; in the one a disk, in the other a spireme. The nucleolus 

 does not fragment directly into chromosomes, as upheld by so 

 many investigators, but only contributes the less dense substance 

 seen at metaphase, which eventually may be discharged or become 

 partially amalgamated with the chromatin. Hence Spirogyra, as 

 regards the constitution and behavior of its nucleolus, need not 

 be placed in a different category from the remainder of the green 

 algae or from that of higher plants. 



LITERATURE CITED 



1. Berghs, J., Le noyau et la cinese chez le Spirogyra. La Cellule 23:53- 

 86. 1906. 



2. Coluns. F. S., The green algae of North America. Tufts College Studies 



3- Digby, L., A critical study of the cytology of Crepis vircns. Archiv 

 Zellforsch. 12: . ph. 8-10. 



