454 SUMMARY OF CURRENT RESEARCHES RELATING TO 



SO closely to these small algw ; and the various methods by which he 

 effected this he describes in detail, as well as the methods of killing, 

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

 prolonged experimentation he at last discovered a method of differentia- 

 ting the granules from the chromatin by means of stains, thus avoiding 

 what had been a source of much confusion to previous authors. The 

 very best differential chromatin stain was found to be freshly prepared 

 Ehrlich's hematoxylin made from Griibler's hsmatin. With this, it is 

 possible to stain the chromatin without affecting the granules. A 

 summary and digest of previous work on Cyanophyce^e cell-structure is 

 given, special attention being devoted to the recently published views of 

 Kohl, Phillips, and Olive, A brief comparative analysis of the con- 

 flicting conclusions of these authors on tlie respective points at issue is 

 added. The lack of unanimity in their results is shown by the author to 

 be due to their failure to differentiate the structures present in the cell 

 and their eagerness to recognise a complicated mitotic nuclear division. 

 Gardner's own study of the protoplast of the Cyanophyce£e-cell has 

 convinced him of the constant presence of the following three structures : 

 (1) A cell-nucleus more or less sharply delimited ; (2) The cytoplasm, 

 extending from the nucleus to the cell-wall, and containing (;{) 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 Cyanophycefe a series of nuclear structures is revealed 

 — passing by very gradual steps from a simple scarcely differentiated 

 form of nucleus, which divides by sim|)le 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 Chlorophyceae and 

 the higher plants. A new type of nuclear division has been discovered 

 by Gardner in Dermocarpa, in which the nucleus breaks up simul- 

 taneously into a large number of daughter-nuclei by a process of amitosis. 

 €ell-division is completed 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 

 substances 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 (probably 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 organised chromatophore is found, the cytoplasm holding the 

 colouring matters. No protoplasmic continuity between the vegetative 

 oells appears to exist. 



Brockmann, C. — Ueber das Verhalten der Plankton-diatomeen des Meeres bei 

 Herabsetzung der Eonzentration des Meereswassers und iiber das Vorkommen 

 von Nordseediatomeen im Brackwasser der Wesermundung. (On the behaviour 

 of raarine plankton-diatoms in diluted sea-water, and on the occurrence of 

 North Sea diatoms in the brackish water at the mouth of the Weser.) 



Wiss. Meeresunters., viii. Abt. (Helgoland, 1906) 15 pp., 7 figs. 



