No. 466.] STUDIES ON PLANT CELL.— VIII. 70 1 



Indeed the entire subject is so confused that it does not seem 

 desirable for us to take it up in detail at this time, especially 

 since these inclusions are apparently all secretions or excretions 

 and not morphological features of the cell. The most compre- 

 hensive discussions of the subject will be found in the papers of 

 Hegler (: 01 ), Kohl (: 03), and Zacharias (: 03).! 



Schizomycetes {Bacteria). — The history of research upon the 

 cell structure of the Schizomycetes has run in large part parallel 

 with that on the Cyanophycese. The clearest results have come 

 from studies upon the larger forms of the sulphur bacteria, 

 especially certain species of Beggiatoa, and on certain forms of 

 Spirillum. The more minute types and pathogenic forms in par- 

 ticular have proved very baffling because of their small size and 

 it can scarcely be said that we fully understand their cell struc- 

 ture. As in the Cyanophycese, investigators of the bacteria fall 

 into two groups : one holding that the Schizomycetes entirely 

 lack a nucleus and the other that there is present a structure, 

 often termed a central body, which is the equivalent of a nucleus. 



Biitschli ('96, : 02) has been the most conspicuous advocate 

 of the latter view. He described and figured clearly a central 

 body in the cells of Beggiatoa, Chromatium, and Spirillum with 

 the same org'anization as given in his account of that body in the 

 Cyanophycese. The central body contains granular material 

 which Biitschli regards as chromatin and the structure is shown 

 in stages of division. Biitschli has no hesitation in giving the 

 central body the value of a nucleus. It lies within a peripheral 



' Since the above was written a lengthy paper by Fischer, " Die Zelle der 

 Cyanophyceen " has appeared [Bot. Zeit., vol. 63, p. 51, 1905), too late to be 

 included in these reviews. Fischer has not changed his conclusions on the chief 

 points as discussed in his earlier papers. The chromatophore is a closed cylin- 

 drical structure ; the cyan^phycin granules are proteid in character ; glycogen and 

 another carbohydrate, anabsnin, are conspicuous substances in the cell; the 

 central body is not a nucleus but the seat of important metabolic processes con- 

 cerned with these carbohydrates, and its contents and behavior in cell division 

 have only a superficial resemblance to nuclear structure and mitosis ; the chro- 

 matin granules of Biitschli, Olive,' and others are masses of anabasnin (a car- 

 bohydrate). Fischer's criticisms are fundamental and it is evident that the 

 morphologists must clearly establish the proteid nature of the central body and 

 its contents (especially the" so called" chromatin granules) before they can 

 expect the acceptance of their conclusions as to its nuclear character. 



