Olive, ]\Iitotic di visioii of tlie iiuclei of the Cyanophyceae. 1 i 



(97) and Massart (02). Among tliose who have asserted that 

 it is a nucleus, wliieli, moreover, divides mitotically, are Scott 

 (87), Bütschli (02), Hegler (Ol) and Kohl (03). Wager (03) 

 believes that the central body divides by direct division; while 

 Ernst (89) and Zukal (94) tliink that each of the many slime 

 giobules represents a nucleus, which divides by simple frag- 

 mentation. 



The theories of Hieronymus (92), Zukal (94) and 

 Chodat (94) are historically interesting and deserve special 

 notice. Chodat thought that the central portion of the proto- 

 plasm of the cyanophyceous cell became vacuolated, or emulsified, 

 and that this appearance, together with the granulär contents 

 of the vacuoles — the cyanophycin granules, the slime giobules, 

 and the .,soluble starch*' — caused the differentation known as 

 the central body. Zukal and Hieronymus have theories 

 which present one point of resemblance to each other. Zukal 

 regarded the slime giobules as the true nuclei, which, according 

 to him, divide, form membranes about themselves, and thus re- 

 present many ..naked cells" within the one cyanophyceous cell. 

 These nuclei, he says, may be formed in two ways: they are 

 either cut off froni the central body or eise they are produced 

 from cyanophycin granrdes, which may be slowly changed into 

 nuclei. And most curious tlieory of all-the central body is itself 

 formed from the fusion of the cyanophycin granules and slime 

 giobules! Thus the central body may on the one liand cut off 

 portions of itself to form cyanophycin granules and slime gio- 

 bules, and on the other hand, it may be itself reformed by 

 fusion of these two kinds of granulär substances! 



Hieronymus calls the central body an „open cell nucleus", 

 as distinguished from the „closed" nucleus of higher organisms. 

 This really means nothing more, in my Interpretation, than that 

 the central body is devoid of the nuclear membrane which is 

 characteristic of the resting nuclei of higher plants. Hiero- 

 nymus says, moreover, that the cyano^Dhydn granules (he probably 

 means here rather the slime giobules, or „red granules") are pushed 

 out from the nucleus, and that they represent the chromatin gran- 

 ules. Herein his theoiy bears some resemblance to that of 

 Zukal. 



We are now prepared to examine more closely the central 

 body, which has occasioned so much confusion and difference of 

 opinion. One of the main arguments of Fischer against the 

 nuclear nature of this body is the fact that it occupies such a large 

 Proportion of the sjDace in the cell. It indeed strikes one at 

 iirst examination that the central body is comparatively large 

 and that the cytoplasmic portion of the cell is relativcly small, 

 as is well shown by longitudinal sections of Oscdlatorla (tigs. 7 

 to 10, 14, 17). • 



In filaments examined as a whole as weU as in sections too 

 deeply colored, the central portion usually stains as is shown in 



Beihefte Bot. Centralbl. Bd. XVIII. Abt. 1. Heft 1. - 



