ZOOLOGY AND BOTANY MICROSCOPY, ETC. 305 



differentiated, the central corpuscles lie at its anterior, and not as usual 

 at its posterior end. The supporting-rod of the future head arises 

 from the idiosome-vesicle and grows downwards into the nucleus, and 

 the nucleus becomes converted into the head. The tail-filament acquires 

 its fin-membrane, and becomes divided into the two threads. Later the 

 sperm seems to separate itself from the remaining vacuolated cytoplasm. 

 The points of importance are, the absence of any change of shape in the 

 central corpuscles, the position of these in the ripe sperm, and the fact 

 that in the spermatid the idiosome does not separate itself from the central 

 corpuscles. 



b. Histology. 



Physics of Cell Life.* — Dr. L. Rhumbler, in investigating the 

 physical aspect of cell life, has studied the distribution of pigment in 

 eggs and young larvae. He accepts the view that protoplasm has a foam 

 structure, and endeavours to explain the distribution of pigment as due 

 to physical stress and strain. Thus, Fischel succeeded in staining 

 living Echinoderm eggs with neutral red, and found that during division 

 the minute coloured granules collected round the nucleus, and in the 

 spindle stage became dumbbell-shaped. Rhumbler explains this phe- 

 nomenon in the following way. During division the nucleus absorbs 

 water from the surrounding foam, the alveoli thus diminish in size, 

 and large bodies, such as yolk-spherules, are squeezed away from the 

 region of pressure. But very small bodies like the stained grauules may 

 cling to the alveolar lamellae, and by the condensation of these they 

 appear to collect round the nucleus. Again, the pigmented sperm- 

 track in the frog's egg may arise from the physical stress produced by 

 the passage of the sperm through the foam in quite a similar manner. 

 The sperm tends to pull the foam framework along with it ; there is thus 

 tension behind it, and as a result there is an outflow of the more liquid 

 contents of the alveoli, and a shrinkage of the lamellae to which the 

 pigment granules cling. In general the author believes that in deve- 

 loping eggs pigment plays no active part, but collects passively in 

 regions of increased pressure and condensation. 



Study of Mitosis in Living Cells.f — Herr J. Sobotta recommends 

 the larvae of Salamandra maculata as suitable objects in which to study 

 karyokinesis in actual process. Especially suitable are portions of the 

 cartilaginous branchial arches examined in salt solution. A karyo- 

 kinetic process can be followed for three or four hours, and the chromatin 

 figures — familiar in stained and fixed preparations — can be demonstrated 

 in the living cell. 



Intranuclear Crystalloids. J — MM. L. Leger and 0. Duboscq note 

 that, while intranuclear crystalloids are well known to botanists, they 

 have not been often recorded in animal cells. In all the adult epithelial 

 cells of the mid-gut (which the authors carefully define) of Gryllus and 

 Gryllomorplia, there are intranuclear crystalloids. These are charac- 



* Arch. Entwickelungsmechanik, ix. (1S09) pp. .-,2-100 (1 p].). See also Amer 

 Nat., xxxiv. (1900) pp. 54-6. 



t SB. Phys.-Med. Ges. Wiirzburg. 1899, pp. 91-4. 



X Arch. Zool. Expe'r.. vii. (1899) Notes et Kevue. pp. xxxv.-xsxviii. (2 figs.). 



June 20th, 1900 y°" 



