ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 243 



ture. What then ? It seems possible that death from high tempera- 

 ture may be due to the accumulation of acid (possibly HgCOg) in the 

 tissues, the rate of formation of this acid being commensurate with the 

 rate of metabolism of the tissues. Thus, animals of the same class 

 having a high rate of metabolism, as measured by oxygen consumption, 

 are more sensitive to heat and to COg than are those having a low rate 

 of metaboHsm. J. A. T. 



Acclimatization and Upper Thermal Death Points. — M. H. 

 Jacobs (Journ. Exper. Zool, 1919, 27, 427-42). Experiments with 

 starfish larvae and Paramecium show that in the former there is prac- 

 tically no acclimatization effect, while in the latter acclimatization occurs 

 even in a short time. A formula is given for expressing the acclimatiza- 

 tion in quantitative form. The surplus resistance gained by Paramecium 

 is very remarkable, rising to forty-three. " The animals have, in other 

 words, added to their normal lives, so to speak, forty-three additional 

 lives by their ability to adjust themselves to the changing environment." 

 In general, the slower rates of temperature increase are more favourable 

 for Paramecium and more unfavourable for starfish larvas than the more 

 rapid ones, and it is suggested that data on upper thermal death points 

 should always include not only the times of exposure to the temperatures 

 in question, but exact statements as to the methods by which these 

 temperatures have been reached. J. A. T. 



Influence of Adrenin on Frog's Melanophores and Retina Cells. 

 —Andrew J. Bigney (Jour. Exp&r. Zool., 1919, 27, 391-6). Adrenin 

 causes a contraction of the pigment in the dermal melanophores and 

 an expansion of that in the retinal cells — processes precisely the opposite 

 of each other. When the optic nerve of one eye was cut close to the 

 brain, the retinal pigment was still expanded after an injection of 

 adrenin, which shows that the drug is very probably carried in the blood. 



J. A. T. 



Bent Tail in Mice. — Ernst Blank {Arch. f. Entivicklungsmech., 

 1916, 42, 333-46, 36 figs.). A detailed anatomical and histological 

 account of a markedly elbowed tail in a race of mice. The bending 

 is due to a partial fusion of vertebras, the result of a process analogous 

 to that which leads in ontogeny to the reduction of the number of caudal 

 vertebrae in a good many mammals. J. A. T. 



Osmotic Pressure of the Blood. — Georc4e G. Scott (American 

 Naturalist, 1916, 50, 641-63). The blood of marine Invertebrates has 

 the same osmotic pressure as the sea-water and the same content of 

 salts. It is the same in a marine Cyclostome. In Elasmobranchs 

 the osmotic pressure is the same, but there is only 1 • 7 p.c. of sodium 

 chloride instead of 3 p.c, urea and other organic compounds making up 

 the difference. Marine Teleosteans, without urea in the blood, show an 

 osmotic pressure half that of the sea-water. Fresh-water Teleosteans 

 and higher animals have a still smaller osmotic pressure. Scott points 

 out that anadromous fishes, like salmon and eel, experience, when they 

 leave the sea and enter fresh-water, a notable reduction (about 18 p.c.) 



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