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were transferred, after little more than an hour, to a shallow glazed 

 earthenware pan, of a circular form, about a foot in diameter, with- 

 out gravel, the water in which, afterwards, was changed daily once, 

 and once only. The vessel was kept in a room of a temperature 

 fluctuating from about 55 Fahr. when highest, to about 40 when 

 lowest. The water used was well-water of considerable purity, and 

 before used it was allowed to acquire the temperature of the room. 



Two modes occurred to me as likely to afford the means of testing 

 the vital power of the ova, or their power of endurance without loss 

 of vitality ; viz. one by subjecting them for a limited time to a tem- 

 perature raised above the ordinary temperature ; the other, by having 

 them conveyed to a considerable distance. 



For the trials first proposed, the ova were put into a thin glass 

 vessel half-full of water, which was placed in a water-bath and heated 

 to the temperature desired. 



The first experiment was made on ova taken from the general stock 

 one day after their expulsion. Six, for two hours, were exposed to 

 a temperature varying from 79 to 80 of Fahr. The result was, 

 that they became opaque in the course of twenty-four hours, all but 

 one, and that, some days after, underwent the same change, denoting 

 loss of vitality. 



The second experiment was made on the 1 Oth of November. Six 

 ova were similarly exposed for two hours to a temperature rising 

 gradually from 70 to 78 ; the result was similar : on the following 

 day they were all found opaque. 



The third experiment was made on the 1 1 th of November. The 

 same number of eggs were exposed for an hour to a temperature 

 falling from 70 to 69. Two shortly became opaque ; four retained 

 their transparency during a month, though in reality dead, which 

 was denoted by their bearing no marks of development when seen 

 under the microscope, those ova which retained their vitality being 

 at that time well advanced. 



The fourth experiment was made on the 1st of December ; the ova, 

 the same number, were exposed to a temperature rising from 75 to 

 78 for an hour and twenty-two minutes. Three became opaque, 

 other three retained their transparency and vitality, and in due time 

 were hatched, the first on the 31st of December, the last on the 7th 

 of January. 



