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^ 1/“. — 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’' 31“. — Nitrate of Potass. Seventy four ova were well bathed witli 
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 in four 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^* 37“. — 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. 
