Olive, Mitotic divisioii of the nuclei o£ tlie Cyanopliyceae. -9 



eontorted sliapes by tlie surroimding cyanopliycin granules; and 

 also to tlie instance given by Raciborski, in wliicli the nuclei 

 of certain seeds assnme irregulär sliapes, due to tlie pressure of 

 tlie granules of food substances. 



Tlie writer may liere be allowed, before leaving tliis subject, 

 to give an opinion wliich lias not yet been at all definitely 

 establislied in liis investigations. It is possible tliat, in the spore 

 of Cylindrospermum shown in fig. 80, the nucleus, whicli is 

 extremely large in comparison with tliose of the vegetative cells, 

 represents in reality several nuclei. Tliere is some evidence that 

 nuclear division continues in the young, developing spores of 

 these plants, iintil about four nuclei are formed; no wall, however, 

 separates tliem. In another species, Cylindrospermum catenatum. 

 walls are at once formed, and \ve have, as a result, several 

 spores borne in a cliaiii, instead of one. The writer hopes to 

 establish these interesting points more definitely by further 

 research. If it be true, however, that there are several nuclei 

 in the spores of this alga, then we can readily understand how 

 such an abundance of chromatin comes to be present. 



Mitosis in Gloeoeapsa j^olf/derniatiea» 



Gloeocapsa presents a peculiar type of cell division which 

 has been, so far as I am aware, nowhere eise observed in the 

 organic kingdom. This plant seems to have been employed for 

 study by bat few investigators since the tinie wollen Schmitz 

 first, in 1879, thought that the granules in the center of the cell 

 represented the nucleus, and, later (80), concluded that he had 

 been mistaken. Sections of young cells are sliOAvn in figs. 62, 

 (54, 69 and 76, all stained witli iron haematoxyliii. Usually about 

 eight clark gi^anules can be counted, which, for reasons which 

 will be explained later, are called chromosomes in the following 

 account, and which are surrounded by an achromatic substance. 

 Minute granules of food material — the „slime globules'' of Schmitz' 

 are abundant in the peripheral proto23lasm. The cytoplasm, in 

 the living cell, also coiitains the diffusecl pale greeii coloring 

 matter. Witliin or close beside the central body may further 

 occur globules of a substance stainable witli haematoxylin; these 

 are, in all probability, the ,, slime globules" of Palla (figs. 62, 

 64, 66 etc.). In examining a preparation stained witli iron hae- 

 matoxylin (which gives mucli better results in this instance than 

 Flemming's triple stain on account of the staining by the latter 

 of the thick, gelatinous wall in which the cells lie), we often 

 find such a spiremc-like arrangement of the chromatin as is 

 shown in figs. 63, 68 and 72. It is possible even to distinguish, 

 in lig. 72, the individual granules, bound together by the linin 

 substance; whereas in figs. 63 and 68, the granules of the thread 

 can not be easily made out, perhaps because of overstaining. 

 In figs. 71 and 75, it is plainly evident that the spireme thread 

 has begun to segment at both onds; and in figs. 67 and 70, a 

 complete longitudinal Splitting has taken place, for we can now 



