No. 466.] STUDIES ON PLANT CELL. VIII. 703 



of Vejdovsky (: 04) describes and figures a simple type of spindle 

 in Bacterium gammeri and Bryodrilus eJilersi with a separation 

 of two groups of chromatin granules during mitosis~ 



The chief critics of the conclusions that the cells of Schizo- 

 mycetes are nucleated have been Migula ('95) and Fischer. 

 The latter author in particular has devoted considerable attention 

 to the group especially in his paper of 1897 which is largely a 

 discussion of Biitschli's ('96) results on studies of the blue-green 

 algae and bacteria. Fischer considers the central body described 

 by Biitschli in the sulphur bacteria as merely a vacuolate region 

 of the cell made conspicuous by the arrangement of the sulphur 

 grains and that the structure does not appear in cells which are 

 free from sulphur. The granular material, considered as chro- 

 matin by others, is regarded by Fischer as reserve material. 

 The central body described by Biitschli in the cells of Spirillum 

 is stated to be a product of contraction. In general the same 

 criticism which Fischer applied to the methods of staining and 

 interpretation of structures in the Cyanophyceae is presented for 

 the Schizomycetes. Fischer cannot justify Biitschli's ('90) view 

 that the smaller bacteria are chiefly composed of nuclear sub- 

 stance, a view which probably has few if any followers to-day 

 and could scarcely claim to be more than a passing suggestion. 

 In short, Fischer finds no evidence of a nuclear structure in the 

 Schizomycetes but curiously ends by declaring that the group 

 has no affinities with the Cyanophyceae but that its forms are 

 closely associated with the Flagellata. 



SaccJiaromycetes (Yeasts]. The structure of the yeast cell 

 has been perhaps the subject of as long a series of investigations 

 as the cells of the Cyanophyceae and Schizomycetes, and the 

 problems in both cases have many similar features. The chief 

 problem in the yeasts has concerned the presence or absence of 

 an organized nucleus or its equivalent in the form of some sim- 

 pler structure. The accounts range from a complete denial of 

 its presence to descriptions of a nuclear apparatus of considera- 

 ble complexity which passes through some rather involved activi- 

 ties during cell division. It is impossible for us to treat the 

 subject historically. We shall only consider the accounts of the 

 most recent investigators and try to determine the probable 



