ZOOLOGY AND BOTANY, MIOBOSCOPY, ETC. 601 



its edges resting on the masses of cytoplasm wMch surround the daughter- 

 nuclei. For this tube Strasburger proposes the term connecting-tube. 



The nucleoli disappear during these changes at an earlier or later 

 period, and take no important part in the nutrition of the nuclear 

 filaments. The chemical changes which take place in the elements of 

 the cellular plate may possibly be due to the influence of the substance 

 of the nucleoli. In cells filled with cytoplasm the cellular plate soon 

 stretches across the whole width of the equatorial plane, and the trans- 

 formation of the dermatosomes into membrane progresses rapidly from 

 the centre towards the periphery. The formation of cell- wall is therefore 

 entirely dependent on the presence of a nucleus. 



Prof. Strasburger finally discusses the question whether the male 

 and female organs in the act of impregnation have the same number of 

 nuclear filaments. He believes that this is the case in the higher plants, 

 and also in the animal kingdom, as shown by observations on nematodes, 

 and that the participation of an equal number of nuclear filaments in 

 impregnation is a very general fact in the organic world ; but it is 

 certainly not without exception. In Avion empiricorum, for example, 

 according to Platner, the number and volume of the nuclear filaments 

 are less in the spermatic nucleus than in that of the oosphere. Union of 

 the nuclei he believes to be essential to the act of impregnation. 



Relation between the Function and Position of the Nucleus.* — 

 Dr. E. Korschelt calls attention to the researches of Haberlandtf on 

 this subject, and confirms, from corresponding facts in the animal king- 

 dom, his conclusion that the nucleus is to be found in that part of the 

 cell which has to supply the greatest portion of the food-material for a 

 growing organ. His examples are taken from the position of the ger- 

 minal vesicle in the ovum of insects, which (in Forficula and Bytiscus) 

 is to be found, according to circumstances, nearest to that part of the 

 ovum in which an absorption of new substances, and very probably also 

 an assimilation of them, takes place on the part of the ovum. Other 

 examples to a similar efiect are adduced. 



Permeability of Protoplasm.^ — In continuation of his investigations 

 on the plasmolysis of Alg8e,§ Dr. J. M. Janse distinguishes between two 

 forms of the permeability of protoplasm for water — intrameahility, or 

 the capacity of the protoplasm to allow of the passage of certain sub- 

 stances into the vacuoles ; extrameahility, the capacity to allow of their 

 exit from the vacuoles. The plants experimented on were chiefly 

 ChsetomorpJia serea and Spirogyra nitida, also the epidermal cells of 

 Curcuma and Tradescantia. 



The use of very dilute solutions of various substances — sodium chloride, 

 potassium nitrate and sulphate, cane-sugar, &c. — and then staining 

 with a solution of diphenylamin in concentrated sulphuric acid, showed 

 that the protoplasts of all the plants examined were intrameable for 

 these substances ; and further, that when the protoplast is intrameable 

 it is not also extrameable. The parietal utricle (Hautschicht) is, on the 

 other hand, both intrameable and extrameable ; this is shown in the 

 excretion of sugar from nectaries, in the secretion and absorption in the 



* Biol, Oentralbl., viii. (1888) pp. 110-8 (8 figs.). 



t See this Journal, 1887, p. 980. 



X Versl. Meded. K. Akad. Wetenscb. Amsterdam, 1888, pp. 332-436 (1 pi.). 



§ See this Journal, ante, p. 93. 



