BACTERIA 93 



characterizes the youngest cells, follows a phase where the cytoplasm 

 becomes alveolar. At this time, at one of the poles of each cell, appears 

 a very large homogeneous granule which Penau regards as a nucleus. 

 This nucleus, however, has only an ephemeral existence and quickly 

 undergoes a cytolysis during which it disintegrates. The disintegra- 

 tion products then impregnate the trabeculae of the cytoplasm and the 

 nucleus becomes diffuse. In a last phase which corresponds to sporo- 

 genesis, the chromatin which impregnates the cytoplasm is partly con- 

 densed at one of the poles, where it forms first a mass of grains, then a 

 large granule which changes to a spore. 



Nothing is less conclusive than these results, since the author cannot 

 discover an homologous structure in the different species which he 

 studies, and since the nucleus which he describes is only a transitory 

 organ not showing the distinguishing characteristics of a nucleus. 



To prove the existence of a nucleus in bacteria, it is necessary to 

 show a nucleus with a differentiated structure, the constant presence 

 of the nucleus, and to follow the division of this organ during the cellular 

 separation. So far no one has apparently been able to differentiate 

 such an organ in well-defined bacteria. We must conclude, therefore, 

 that with the exception of the results obtained by Vejdowsky, all ob- 

 servations so far gathered in favor of the existence of a typical nucleus 

 in bacteria are by no means convincing. 



The third theory asserts the existence of a diffuse nucleus in bacteria. 

 It was first suggested by Weigert and more carefully formulated by 

 Blitschli. This author describes in a certain number of Sulpho-bacteria 

 of large size, Beggiatoa, Chromatium, a kind of central body occupying 



FIG. 72. i. Chromatium okenii. 2. Beggiatoa alba. These two bacteria have 

 a central body containing chromatic grains and considered by Biitschli as the 

 equivalent of a nucleus. (After Biitschli.) 



nearly the whole volume of the cell and consisting of an alveolar cyto- 

 plasm of highly stainable web, containing within its knots numerous 

 chromatic granulations (Fig. 72). The remainder of the cell consists 



