• ATYPICAL MITOSIS AND OTHER NUCLEAR PHENOMENA 193 



times aggregate to form groups with a plastid-like appearance. Ergastic 

 substances, such as glycogen, fat globules, and "cyanophycin granules," 

 also occur and vary in abundance under different nutritive conditions. 

 Although the cytoplasm is rich in lipides, no chondriosomes are present, 

 according to Guilliermond. This author describes a vacuome consisting 

 of small vacuoles containing metachromatin, the precipitation of this 

 substance giving the granules mistaken for nuclear matter by certain 

 observers. 



It is tempting to search among lowly organized plants for light on 

 the origin of structures and modes of behavior seen in more complex 

 types. Although it is improbable that the Cyanophycese had anything 

 to do with the evolution of higher plants, the organization they exhibit 

 affords a hint as to stages which may have occurred in the evolution of 

 the typical nucleus and its elaborate mode of division. The view has 

 long been entertained that certain leading constituents of primitive 

 protoplasm may gradually have aggregated to form a definite organ, the 

 nucleus, thus securing the advantages of more consistent interaction and 

 orderly distribution during growth and differentiation. By arranging 

 various blue-green and other algse in a suitable series, one can at least 

 illustrate "the conception of cell structure which implies differentiated 

 regions of a colloidal system in which special processes have become 

 localized and tend to remain fixed" (Harper, 1919). 



Bacteria. — The bacterial cell presents many obstacles to cytological 

 study. It is extraordinarily small and is often surrounded by a layer of 

 material which interferes with fixation; moreover, it contains ergastic 

 substances which vary in amount and present a great variety of aspects in 

 different preparations. Opinion has ranged all the way from the view 

 that the whole bacterium is a naked nucleus to the idea that it is wholly 

 cytoplasm with inclusions. Most prevalent has been the view that 

 scattered nucleo-proteins are present but not aggregated into a definite 

 nucleus, the cell thus illustrating a primitive stage in the evolution of the 

 nucleus-and-cytoplasm type of organization.^^ 



The literature contains many descriptions of small granules supposed 



to be nuclei or at least granules of "nuclear matter," and the aggregation 



of such granules to form peculiar spiral masses has frequently been 



reported. The spiral masses seem to be modifications of the cytoplasm 



about the vacuoles (Meyer), while the nature of the supposed nuclei 



has been rendered doubtful in most cases by the presence of ergastic 



masses which may simulate nuclei. In Bacillus pasteurianus, Meyer 



regarded as nuclei certain minute bodies which he was able to distinguish 



from the globules of fat, volutin, and glycogen. The frequently paired 



arrangement of such small bodies was suggestive of division, and their 



33 See the accounts by Meyer (1912), Dobell (19116), Frost (1917), Lohnis (1922), 

 Kirchensteins (1922a), Enderlein (1925), Petit (1927), and Wdmoscher (1930). 



