698 THE AMERICAN NATURALIST. [VOL. XXXIX. 



Other authors as Scott ('88), Hegler (:oi), Butschli (: 02), 

 and Kohl (: 03), also believe that the central body is a nucleus 

 which divides mitotically but none has described the process as 

 so closely similar to nuclear division in higher plants as in the 

 account of Olive. Some of their results are criticized by Olive 

 as based on preparations in which the stain was not properly 

 differentiated or the sections were too thick. Among the recent 

 writers Wager (: 03) stands alone as holding that the nucleus 

 divides directly (amitotically) by a process of simple fission. 

 Both Kohl and Wager conceive the chromatin as in a network 

 or convolute spirem which breaks up into segments which are 

 drawn apart, thread by thread, quite a different process from the 

 splitting of organized chromosomes. Other authors have held 

 that the granules in the central body were chromatin although 

 they were not willing to admit the structure as a nucleus. Thus 

 Macallum ('99) found that the central body contained phosphor- 

 ous and "masked iron" to a conspicuous degree and he, with 

 other investigators, has shown that this structure resists the 

 action of artificial gastric juice, solutions of pepsin, etc. These 

 chemical reactions are considered confirmatory of the theory 

 that the granular material is a proteid of a high order of or- 

 ganization such as would be expected of chromatin. However, 

 such chemical tests are very difficult to apply and do not seem to 

 the writer so important in establishing the nature of the central 

 body as does the careful study of its structure and activity during 

 cell division. The objection that the central body lacks a mem- 

 brane, universally present around resting nuclei of higher plants, 

 is not regarded as vital by Olive. In the first place such a 

 membrane may be found around the resting nuclei in young 

 heterocysts and spores and its absence in vegetative cells is 

 probably explained by the rapidity of the successive cell divi- 

 sions. There are some recent writers, as Massart (: 02) and 

 Zacharias (: oo, : 03) who are still unconvinced that the granules 

 in the central body are chromatin and that the structure is the 

 equivalent of a nucleus. Their papers and figures, however, 

 clearly show that they have failed to find the detailed structures 

 of other investigators. 



Fischer ('97) has been the most conspicuous opponent of the 



