﻿,V-2 



BOTANICAL GAZETTE 



from the cytoplasmic material, blends with a from the equa- 

 torial disk. Since disk c with a plays an important part in the 

 reconstruction of the nucleus, and only disk a seems to coincide 

 with the amalgamated chromatic material seen on the slides, it 

 would appear that Spirogyra lends support to the views of those 

 who believe that the chromosomes are not the sole containers of 

 hereditary substances. It cannot be said that the material of the 

 mother nucleus is equally divided between the two daughter nuclei, 

 for all of the material in the two nuclei is not from the mother 

 nucleus ; while again, some of the colloidal material of the mother 

 nucleus passes into the cytoplasm before the two daughter nuclei 

 are formed. These observations also suggest that karyokinesis 

 is no longer to be considered merely as a process of division, but 

 as a process made up of alternating phases of addition, combination, 

 and withdrawal of protoplasmic substances from nuclear centers. 



Summary 



Instead of a spireme, as in 5. crassa, a disk arises from material 

 condensing within the mass of nuclear plasm and central body. 

 This disk is discernible in both living and stained material. 



No trace of organization is to be seen in the living disk, but 

 fixed material shows it to arise from aggregations of variable 

 appearance and staining qualities. These aggregations are not 

 the chromosomes. The more deeply stained of these bodies arise 

 from the nuclear plasm, the less deeply stained appear to come 

 from the decomposing central body. 



This sphere of aggregated material gradually changes in shape, 

 becoming a cylinder. The more deeply stained masses become 

 arranged upon it as an equatorial band. This band is homologous 

 with the disk seen in living material. As the disk evolves, chro- 

 •matic bodies, averaging 14 for this species, are to be seen on the 

 band, while other irregular masses of chromatic material project 

 as loops or pyramidal masses from its edge. These loops or masses 

 represent material from nuclear plasm and central body that has 

 partially amalgamated. 



No rift appears in the living disk to indicate a sharp splitting 

 of components, but instead the changes in appearance indicate a 



