ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 87 



only), are or are not inclosed by a distinct membrane. He claims to 

 be able to answer this question definitely in the affirmative, the best 

 results having been obtained from Spirogyra nitida. 



The method employed was by the action of a 10 per cent, solution 

 of potassium nitrate, which absorbs water very rapidly from the cell- 

 sap, or ph\smolyses the cell. When the parts begin to become dis- 

 organized in this solution, the vacuole-membrane remains the longest, 

 the vacuole lying like a ball in the cell, the membrane retaining its 

 tension, and being especially well seen if the potassium nitrate is first 

 coloured by eosin. The author regards the vacuole-membrane as a 

 special organ present in all cells, at least during a certain period of 

 their existence, which has for its function the production of turgidity 

 in the cell ; and for this organ he proposes the term Tonoj)last. 



Distribution of Protoplasm in the Curved Parts of Plants.* — 

 Herr F. G. Kohl has observed that in curved parts of plants the 

 protoplasm behaves differently in different organs, with respect to its 

 sensitiveness to light. In the root-hairs of Trianea hogotensis, which 

 are very transparent, and the protoplasm of which is in active motion, 

 this substance always accumulates at those spots only which are 

 exposed to the most intense light. On the other hand, in the hairs 

 on the tigellum of seedlings of Sinapis alba, the protoplasm moves 

 from the walls which are directly illuminated to those in the dark. 

 In curved organs like climbing stems, tendrils, &c., the protoplasm 

 accumulates most on the concave side. 



Structure of the Cell-nucleus, f — M. C. van Bambeke gives a 

 useful resume of the present state of our knowledge of the structure 

 of the cell-nucleus when in a state of rest, as derived from the 

 observations of the most recent investigators. 



Division of the Cell- nucleus in Tradescantia.t— In the epidermal 

 cells and those of the hairs on the stamens of Traclescantia virgimca, 

 and in the mother-cells of the pollen, M. E. Bernimoulin finds the 

 nucleus at first granular, and inclosing a large number of chromatic 

 rods, which then coalesce so as to form one or more knotted threads. 

 The contour of the nucleus then disappears, the chromatic thread 

 unrolls, spreads through the protoplasm of the cell, assumes the form 

 of a nuclear plate, and divides into a certain number of segments, 

 which curve and separate into two groups to form the new nuclei. 



Chemistry of the Cell-nucleus.§ — Herr A. Kossel has carefully 

 investigated the chemical composition and pro2)erties of the chromatin 

 of the nucleus of animal and vegetable cells, and finds it to be 

 identical with nuclein. If nuclein is heated with dilute sulphuric 



* Wigand's Bot. Hefte, 1. (1885) p. 161. See Naturforscher, xviii. (1885) 

 p. 337. 



t Bambeke, C. van, ' Etat actuel de nos connaissances sur la structure du 

 noyau cellulaire a I'etat de repos,' 34 pp., 8vo, Ghent, 1885. 



X Bernimoulin, E., ' Note sur la division des noyaux de Tradescantia virgimca' 

 10 pp. (2 pis.), Gand, 1884. See Bull. See. Bot. France, xxxii. (1885). Eev. Bibl., 

 p. 102. 



§ Ber. Deutsch. Chem. Gesell, xviii. (1885) p. 1920. See Naturforscher, 

 xviii. (1885) p. 376. 



