THE OVUM IN THE AMPHIBIA. 231 



remaining ova, both in No. 3 and 4, were destroyed. Many of the yelks had begun 

 to change form within the first hour, and the envelopes exhibited the same refractive 

 appearance as in the previous experiments. 



Anticipating from the former experiments what probably might be the ultimate 

 result in these, I now determined to put beyond the possibility of doubt, both the 

 fitness of the seminal fluid employed to effect impregnation and the healthiness of 

 the ova, and their susceptibility to become impregnated ; and to show from these 

 facts that a non-production of the embryo in this set of experiments must be due to 

 the action of the potass solution, and not to any unfitness in the spermatozoa or the 

 ova. Accordingly, 



No. 5. P.M. 3 h 17. Sixty-two ova, from the same female employed in the pre- 

 ceding experiments, were bathed with a portion of the seminal fluid and water which 

 had been employed in No. 1 and 2, and were then placed side by side with these, in 

 a separate dish. 



At the expiration of four hours and thirteen minutes, the temperature being 60 

 FAHR., from thirty to forty of these ova had become segmented. Some of the ova 

 had been injured mechanically, but nearly the whole that had not been injured were 

 impregnated. On the seventh day there were twenty-three embryos, thirteen of which 

 had already left the egg-envelopes ; others were somewhat less advanced, thus proving 

 the fitness of the seminal fluid to impregnate, and the ova to produce. The number 

 of embryos too was fully as great as could have been expected, seeing that many of 

 the ova had been slightly injured, and that the seminal fluid had already been one 

 hour and twenty-six minutes mixed with water. 



The result of this experiment was borne out by the following. 



No. 6. P.M. 3 h 31 m . Nitrate of Potass. Seventy-four ova were well bathed with 

 impregnating fluid and water on a previously dry surface, and one second afterwards 

 with a strong solution of nitrate of potass (twenty grains to one ounce of water), and 

 water was then added to them ; the whole time of the experiment being twenty 

 seconds. 



No. 7- Fifty-nine ova were treated in exactly the same way, save that the interval 

 between the application of the impregnating fluid and the solution of potass was 

 three seconds, and the whole period twenty-five seconds. 



Segmentation commenced in each of these sets \nfour hours and fourteen minutes, 

 when from twelve to fifteen ova were undergoing this change in No. 6, and thirteen 

 in No. 7- At a later hour there were many more in each experiment only very par- 

 tially segmented, and which proved to be unproductive. At the end of the seventh 

 day there were twelve embryos in No. 6 advanced to the same stage as in the simply 

 artificial impregnation No. 5, and ten embryos in No. 7, but at a little less early stage 

 of growth, a circumstance which I attributed at the time to imperfect aeration. 



No. 8. P.M. 3 h 37 m . Seventy-nine ova were bathed with the same solution of nitrate 

 of potass as above, and three seconds afterwards with impregnating fluid in water; 

 the whole time occupied being twenty seconds. 



