ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



867 



when one died. In C, in wliicli the aquarium water was changed 

 daily, and light shut off, the three specimens died on the 105th, lOGth, 

 and 109th days ; B, in which the water was not changed, and which 

 was exposed to the light, only lost one specimen, and that on the 

 100th day. , „ , t 



Dr. Graff concludes that the algfe or pseudo-chlorophyll bodies 

 of Hydra have no significance as means of nutrition ; the fact that all 

 the specimens in filtered water died by the 87th day seems to show 

 that the Hijdr(B died from the want of animal food, and that the 

 green bodies do not serve as such, as Brandt supposes. The most 

 unexpected and perhaps the most remarkable fact is that, whether the 

 Hydrce were exposed to the light or placed in the dark, they in all 

 cases retained their green colour throughout life. 



Dr. Graff has lately been able to make some observations on the 

 rare Mesostoma viridatim, three out of five examples of which were 

 richly provided with chlorophyll-corpuscles ; these varied very con- 

 siderably in size, and no nucleus was to be detected in the smaller 

 specimens; starch granules of proportionate size to that of the 

 chlorophyll bodies were found in them. The larger green bodies 

 were arranged in closed groups, and the smaller examples lay between 

 the groupsl most of the bodies were rounded, but a few of the larger 

 were oval. 



Action of High Pressures on Putrefaction and on the Vitality of 

 Micro-organisms.*— A. Certes has endeavoured to solve the problem 

 which he has already touched upon,t as to the processes and conditions 

 by which organic matter is restored to the inorganic condition at the 

 bottom of the sea. 



In his experiments he endeavoured, as far as possible, to keep to 

 the conditions of nature, and by a special arrangement succeeded in 

 avoiding sudden changes in pressure. The greater number of the 

 experiments were made at 350 to 500 atmospheres, which corresponds 

 to the pressure of the average depths registered in the ' Travailleur ' 

 and ' Talisman ' expeditions. Owing to the warmth of the season the 

 author was not able to repeat his experiments at the mean tempera- 

 ture, of great depths, + 4° C, but he is able to assert that the 

 phenomena of putrefaction are invariably produced in infusions of 

 very different kinds, which he cultivated under pressure. In all of 

 them, after a certain time, the liquid becomes cloudy, the organic 

 substances, animal or vegetable, disappear, and microscopical ex- 

 amination reveals an abundant development of _ microbes. This 

 development is, however, slower than in the open air. 



The author points out certain peculiarities arising from com- 

 parative experiments— for instance, on the 13th of June two tubes 

 with a vegetable infusion in fresh sea water were put, the ono under 

 a pressure of 350 atmospheres, the other left in the air served for 

 control. The apparatus was inspected every day, and the pressure 



♦ Comptc8Rendn8,x<ix. (1884) pp. 385-8. . , . . , ,,, 



t Seo tlilH Journal, ante, |). 317 (2nd note). Ihc footnote X should have 

 contained a reference to (Joniptca KcnduH, xcviii. (1884) p. 690. 



