242 PROCEEDINGS OF SOCIETIES. 



rotifers used were first dried by fifteen days' exposure to a burning 

 sun ; tbey were tben kept in the shade at a temperature of 18° C. for 

 another fortnight, and subsequently from July to October under the 

 receiver of an air-pump, with quick-lime, showing a pressure of only 

 3 mm. In October he found half the rotifers thus treated capable of 

 revival, which he accounted for by the quantity of earthy matter 

 mixed up with them, and the average low temperature of the season 

 during their sojourn under the pump. All the tardigrades associated 

 with the rotifers died. The final experiment at complete desiccation 

 was made with two decigrammes of the rotifers and sand that had been 

 in the air-pump. 



He cites Claude Bernard, saying, in 1864, " that infusoria ordi- 

 narily (convenablement) dried lose their vital property, at least in 

 appearance, and may remain so for whole years ; but when supplied 

 with a little water, they become as lively as before, provided that a 

 certain degree of desiccation has not been exceeded." 



I have also a reference to a paper by Gavarret, Ann. des Sci. Nat. 

 (Zool.), vol. xi., 1859, relating to " dessiccations afroid" et " chauffes," 

 in which he speaks of "the coagulation of hydrated albumen as 

 speedily fatal to most organized beings." 



The whole question, in fact, turns upon the amount of desiccation ; 

 and no chemist, accustomed to analysis, would consider an organic 

 substance really dry until it had been sufficiently exposed to air that 

 had passed through some desiccating material, and heated to 212° F. or 

 more. No chemist would have expected to dry the rotifers by the 

 process which did not succeed. Professor Miller mentioned 212° to 

 250° as the temperatures generally required to dry organic matter, and 

 when the greatest possible dryness is required, the heat should, as 

 long ago pointed out by Faraday in his ' Chemical Manipulation," 

 only stop short of charring the material. 



I remain, Sir, yours obediently, 



Henry J. Slack. 



PROCEEDINGS OF SOCIETIES. 



Kotal Microscopical Society. 



King's College, April 2, 1873. 



Charles Brooke, Esq., President, in the chair. 



The minutes of the preceding meeting were read and confirmed. 



A list of donations to the Society since the last meeting was read, 

 and the thanks of the meeting were voted to the donors. 



Mr. Henry Davis read a paper " On a New Callidina : with the 

 Result of Experiments on the Desiccation of Rotifers." The paper was 

 illustrated by a carefully-executed drawing of the new species 

 (C. vaga), and by living specimens exhibited under the microscope. 

 (The paper will be found printed at pp. 201-209). 



