Olive, Mitotio divisioii üf tlie unclei of the Cyanophyceae. 19 



down (ligs. 82 and 83). In Gloeocap.sa poJydermatica Kützing 

 (figs. 62, 64, 76), and Nostoc commune Vaucker, eight chromo- 

 somes could nsually be counted. In OsciUafona tenuis Agardli 

 flg. 4\ OsciUaioria sp. (figs. 15, 26, 27), Phormidiuiw sp. (figs. 32, 

 33 j, Calothrix tJiennalis Hansgirg^) (fig. 43), tliere are sixteen 

 chromosomes. 



Tlie cells in OsciJJatoria Froellcliia Kützing and 0. prin- 

 ceps Validier are so sliort tliat tlie central body takes on the 

 form of a flattened disc, appearing in section as sliown in tbe 

 figs. 7 — 13. Tlie shallowness of tlie nucleus undoiibtedly accounts 

 for tlie difficiüty in determining definitely the niimber of the 

 chromosomes, since tliose whicli beloiig to the lower group may 

 easily be counted witli those in the upper focus. Tliere are, 

 however, in all probability, thirty two in the cells of these two 

 species, although for a long time I thoiight there were about 

 twice that iinmber (figs. 18, 24). 



In those cells in wliich there are sixteen chromosomes, one 

 may usually count in median longitiidinal view three or four 

 (figs. 2, 6, 14, 17, 34, 37); while in the two large Oscillatorias^ 

 we may frequently see as many as eight in side view (figs. 7, 

 10). Tliis fact leads one to the conclusion that Tolypothrix also 

 has sixteen chromosomes, since botli Kohl and Wager show 

 in tlieir draAvings about four or five in median section; this 

 opinion is, however, at variance wdtli that of Kohl, wlio liolds 

 that the cells in Tolypoihrix contain but four to six. 



It will be noticed, in most of the drawings of longitiidinal 

 sections of the various filamentous forms (figs. 8 — 13, 17, 34, 37) 

 that there is sliown, in some cases much more clearly than in 

 others, minute fibrillar projections from the central body. These 

 are seen in one drawüng only (fig. 12) to run from the central 

 body completely to the cross walls. In certain instances in 

 which the bleaching of the stain has been carried a step too 

 far, these fibrils are not at all visible (figs. 6, 7). In fig. 12, 

 the combination of iron haematoxylin with eosin and the failui'e 

 to wasli the stains out sufficiently have resulted in a black, un- 

 differentiated central portion, and a reddish cytoplasm. The 

 fibrillar projections. in this instance, and the tliin, delicate cyto- 

 plasmic layer liiiing the cross walls, as well as the peripheral 

 chiomatophore, are all stained red with the eosin. We can iiow 

 observe that the projections are connected at their outer ex- 

 tremities with the lining layer of protoplasm along the cross 

 partition Avalls, and further. that at the central body end, each 

 is joined with a chromosoiiie (figs. 8, 10. 17, 34, 37). In the 

 Spaces between the fibers, as will be explained later, are granules 

 of reserve food, the cyanophycin granules (see fig. 21). There 

 remains no doubt in the mind of the writer that these fibrillar 

 ])n)j('i'tions represent the mantle fibers, or „Zugfäsern" of the 

 luitotic figure. They are attached to the wall at the one end 



1) Ivindly determined hy Prof. O. Ki reim er. 



9* 



