CYTOLOGICAL STUDIES IN CYANOPHYCEiE 285 



fixing, and staining which he found to be the most successful. 

 By prolonged experimentation he at last discovered a method of 

 differentiating . by staining-reagents the granules from the chro- 

 matin, thus avoiding what had been a source of much confusion 

 to previous authors. The very best differential chromatin-stain 

 proved to be Ehrlich's hematoxylin, freshly prepared, made from 

 Griibler's haematin. With this it is possible to stain the chromatin 

 without affecting the granules. 



An excellent summary and digest of previous work on Cyano- 

 phycece cell-structure is given, special attention being devoted to 

 the recently published views of Kohl, Phillips, and Olive. A brief 

 comparative analysis of the conflicting conclusions of these authors 

 on the respective points at issue is added. The lack of unanimity 

 in their results is shown by Dr. Gardner to be due to their failure 

 to differentiate the structures present in the cell, and their eagerness 

 to recognize a complicated mitotic nuclear division. Dr. Gardner's 

 own study of the protoplast of the Cyanophycece- cell has convinced 

 him of the constant presence of the following three structures : 

 (1) a cell-nucleus more or less sharply delimited; (2) the cyto- 

 plasm, extending from the nucleus to the cell- wall, and containing 

 (3) the granules. He treats of each of these structures in detail. 

 The nucleus, being large, has its shape influenced by that of the 

 cell. And the author shows that in the Oyanophycece a series of nuclear 

 structures is revealed— passing by very gradual steps from a simple 

 scarcely differentiated form of nucleus, which divides by simple direct 

 division, up to a highly differentiated form, which in dividing shows 

 a primitive type of mitosis, and approximates in structure to the 

 nucleus of the Chlorophycece and the higher plants. A new type of 

 nuclear division has been discovered by Dr. Gardner in Dermocarpa, 

 in which the nucleus breaks up simultaneously into a large number 

 of daughter nuclei by a process of amitosis. Cell-division is com- 

 pleted in the filamentous forms by the gradual ingrowing of the 

 ring-shaped cell-wall. In some cases the division of the chromatin 

 seems to precede the ingrowing of the cell-wall ; in others it 

 accompanies and keeps pace with it ; and in still others it is, as it 

 were, passively constricted and cut in two by the ingrowing cell- 

 wall. In its structure the nucleus consists of granules, chromatin, 

 and an achromatic ground substance in which the two former sub- 

 stances are imbedded. The author demonstrates two kinds of 

 granules in the cell — one associated with the chromatin in the 

 nucleus, and never found in the mature spore ; and the other (pro- 

 bably food material) often present in the vegetative cell, but always 

 present in the mature spore. One of the products of assimilation 

 is glycogen. No definitely organized chromatophore is found, the 

 cytoplasm holding the colouring matters. No protoplasmic con- 

 tinuity between the vegetative cells appears to exist. 



It is impossible in so limited a space to render an adequate 

 account of the results set forth by Dr. Gardner in this important 

 and illuminating addition to our knowledge of the minute structure 

 of the Cyanophycea. 



A. & E. S. G, 



