Vol. 2] Gardner. — Cytological Studies in Cyanophyceae. 279 



moved with alcohol, however, without seriously injuring the cell 

 structure, if the material is previously killed in potasium iodide- 

 iodine or in Flemming's solution. Figs. 28 and 29 respectively 

 represent optical longitudinal and cross sections of Beggiatoa 

 araclinoidea, killed in Flemming 's solution, dehydrated in alcohol 

 until all of the sulphur was dissolved out, and then stained with 

 Loeffler's methylene blue. By this treatment the protoplast is 

 seen to consist of a regular coarse network uniform throughout 

 the cell, with the exception of a very narrow zone next to the cell- 

 wall. This seems to indicate a slight differentiation of the pro- 

 toplast in the direction of the simplest differentiation found in 

 the Cyanophyceae, such as represented by Fig. 1. Iron haema- 

 toxylin and some other chromatin stains differentiate the cell 

 structures in the same manner. As to the differentiation into 

 two zones, my results correspond quite closely to Biitschli's in- 

 terpretation of the structure of Beggiatoa alba, with the differ- 

 ence, however, that in my preparations the "central body" does 

 not appear homogeneous, but consists of a network which occa- 

 sionally extends to the cell membrane. I am not prepared to say 

 whether this network contains chromatin or not. It seems quite 

 probable that it does contain chromatin, however, for Macallum 

 has shown that iron and phosphorus, the essential elements of 

 chromatin, are distributed throughout the cell. Should it prove 

 to be true that this network does contain chromatin, then the 

 coarse network could well be looked upon as the analogue of a 

 nucleus, and in this species only a slight differentiation has taken 

 place between it and the peripheral cytoplasm. There is not a 

 very great gap between this condition and the one found in the 

 differentiation in Oscillatoria margaritifera. Other forms will 

 doubtless be found in which the difference in structure will be 

 even less than the difference between these two species. 



In Beggiatoa mirabilis there are in every cell a few granules 

 which react in the same way to stains as the a granules in the 

 nucleus of the Cyanophyceae, and these are not affected by the 

 stains which color the (3 granules found in the cytoplasm of the 

 Cyanophyceae. There is undoubtedly a close genetic connection 

 between the Beggiatoas and the homocysted forms of Cyanophy- 

 ceae, particularly the Oscillatorias. 



