ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 567 



to dyes and crystalloids, the whole emphasis being placed on the proper 

 ties of a hypothetical plasmatic membrane which is believed to be 

 fundamentally different from the deeper parts of the cells. He has 

 studied the permeability of the internal cytoplasm in eggs of starfish 

 and other marine animals, muscle-cells of Necturus, cells of Spirogyra, 

 and other cases. 



He finds that the structural components of protoplasm vary greatly 

 in their permeability to water, dyes and crystalloids ; that impermeability 

 or partial permeability to water, dyes and crystalloids is a property of all 

 portions of protoplasmic gels ; that the rate of penetration of protoplasm 

 by dyes and crystalloids is, in general, inversely proportional to the 

 concentration of the living gel ; that the best vital stains known pene- 

 trate very slowly into such highly concentrated protoplasm as the 

 epithelial and striped muscle-cells of Necturus ; that the interior 

 portions of the cytoplasm of the starfish egg, and probably the striped 

 muscle-cell of Necturus, exhibit the same sort of osmotic properties as 

 the surface. 



Pyloric Musculature in Bears.* — H. Neuville gives a comparative 

 account of the muscular specialization of the pyloric apparatus in different 

 species of bears. In this respect the Ursidas occupy an isolated position 

 among Carnivores, but the polar bear is an annectant type towards 

 Canidee or perhaps towards Subursidre. The pyloric musculature serves 

 as a triturating apparatus as well as for constriction and dilatation. It 

 reaches in Ursidas a rare degree of perfection as compared with most 

 other Mammals. 



Integument of Plectognaths.f — Nils Eosen has studied a number 

 of types. In all cases the corium consists of two distinct strata, an 

 external one with abundant cells and few fibres, an internal one very 

 rich in fibres. The fibres of the internal layer are arranged in bundles 

 running in varying directions. In Mold, in which this part of the 

 corium is enormously developed, the bundles have a winding irregular 

 loop, and the corium becomes hard and tough. In Tetrodontidas and 

 Diodontidae the bundles are also winding, but not so irregular, so that 

 the skin is extensible. In Ostraciontidas and Balistidas the bundles are 

 arranged in horizontal and vertical laniellre. 



In Molidae and Ostraciontida3 the integumentary ossifications are 

 large plates, which are connected with one another, and project in long 

 spines or short tubercles, more or less piercing the epidermis. This is 

 regarded by Rosen as the most primitive condition. In Balistidte there 

 are plates with small tubercles ; the plates do not touch one another ; 

 they have an oblique vertical position as in ordinary Teleosts, but there 

 are no scale-pockets. In some Balistidae reduction of plates begins, and 

 this reduction is most marked in Tetrodontidae and Diodoni here 



the plate is comparatively minute, while the spine is long. The reduc- 

 tion of the plates into spines is intimately connected with the de- 

 velopment of the air-sac. In all the ossifications two layers can be 



* Ann. Sci. Nat. (Zool.) xx. (1915) pp. 1-38 (3 pis. and 12 figs.), 

 t Arkiv Zool., viii. (1913) No. 10, pp. 1-29 (5 pis. and 8 figs.). 



