AND ON THE DIRECT AGENCY OF THE SPERMATOZOON. 243 



envelopes, and the distension of the tissue with fluid, rather than to the loss of vitality 

 in the contents of the yelk. 



This view has led me to endeavour to ascertain more precisely than heretofore, 

 fast, at what length of time, after immersion in water, the egg usually becomes 

 insusceptible of impregnation ; and next, to what extent the act of fecundation is 

 accelerated by a given increase of temperature, when the experiments are made with 

 portions of fluid from the same male, and with eggs from the same female, at, as 

 nearly as possible, the same time, all the conditions being similar except in regard to 

 the temperature of the surrounding medium. 



With this object, I have recently made two sets of observations consisting each of 

 nine experiments. One set was conducted in a room, the temperature of which was 

 raised artificially to 61 FAHR., and the water in which the eggs were immersed to 

 60 FAHR. ; while the other was carried on in an adjoining room where the tempera- 

 ture was only 55 FAHR., and the water employed 53 FAHR. In order to place the 

 whole of the experiments under as similar conditions as possible, it was necessary 

 that the corresponding experiments in each set should not only be made at about the 

 same time, but should also be supplied with fluid in exactly the same state, and the 

 eggs be immersed in like quantities of water, for the time specified in each experi- 

 ment, before the addition of the fluid. When the time of immersion had elapsed the 

 water was quickly withdrawn, and the fluid poured over the eggs, and fresh water 

 was immediately supplied to them. As much time was unavoidably occupied in 

 passing the eggs into their respective vessels, and noting the period of immersion, it 

 became necessary to commence the experiments with those which had been longest 

 in water, in order that the fluid supplied to the whole should be as nearly as possible 

 in the same condition, in each experiment, at the moment of its application, and be 

 furnished to the eggs in similar quantities. To ensure this, the fluid was mixed, as 

 soon as it was obtained, with fifteen times its quantity of water, and was employed 

 at about thirty-Jive minutes afterwards. The quantity of this mixed fluid poured over 

 the eggs of each experiment was ten minims by measure, excepting only to the first 

 and second experiments of each set, to which twenty minims were added; but even 

 with this advantage, as was seen, with no more favourable change in the result. 

 After the end of the first hour, the eggs which had remained in the lower temperature 

 were removed to the higher, and the two sets of experiments were then placed side 

 by side to watch the time of commencement of segmentation, as indicatory of the 

 more or less accelerated impregnation. The number of embryos subsequently pro- 

 duced showed the ratio in which the eggs had been fecundated after different periods 

 of immersion*. Each set consisted of nine separate experiments, the time of immer- 

 sion of the eggs being forty-five, thirty-five, twenty-five, fifteen, ten, seven, five, three, 

 and one or two minutes in each. 



At the highest temperature, 61 FAHR. atmosphere, and 60 FAHR. water, a tem- 

 * For the details of the experiments, see MS. paper in the Archives of the Society. 



MUCCCLIII. 2 K 



