THE OVUM IN THE AMPHIBIA. 
227 
No. 3 . p.M. 50 “. — Forty-seven ova were passed on a dry surface, and spermatic 
fluid was instantly applied to them, and within ten seconds afterwards the ova were 
washed with the solution of potass, which was allowed to remain, and water was then 
added. At the end of the eighth day not a single embryo had been produced. The 
difference between this experiment and the above was the non-removal of the potass, 
and the more free bathing of the ova. 
No. 4 . p.M. 53 “. — Forty-jive ova were passed on a dry surface, and were jirst 
bathed with solution of potass, and then with seminal fluid in water, and afterwards 
they were removed with No. 1 and 2, to higher temperature. 
At the expiration of the eighth day three embryos had been formed. This result at 
first appeared to be more diflicult of explanation than the former. But, when the 
circumstances are considered, it seems to admit of quite as easy an interpretation. 
The bathing of the ova freely with seminal fluid mixed with water, seconds after 
the application of the solution of potass, diluted this solution too much to allow of 
its effect on the whole of the spermatozoa applied to the ova, while this very dilution 
enabled the impregnating influence of these bodies to take effect in some of the ova. 
The fact, however, leads to an inference of some importance with reference to the 
action of the potass on the envelopes of the ovum, and seems to show that this 
action is less immediate on the envelopes than on the spermatozoa. 
No. 5. Fifty-nine ova were bathed with seminal fluid and water, and Jive seconds 
afterwards with a solution of nitrate of potass (in the proportion of twenty grains of 
the salt to one ounce of water), and water was then added to them. 
No. 6. Seventy-two ova were treated in precisely the same way. 
Not one embryo was produced in either of these experiments. 
No. 7- Forty-four ova were washed with diluted acetic acid immediately after they 
had been shed from the female, and Jive seconds afterwards, seminal fluid with water 
was added to them. 
No. 8. Seventy-sir ova were washed with diluted acid, and treated in every way as 
in No. 7. 
Not a single embryo was produced in either of these trials. 
The action of acetic acid is almost instantaneous on the envelope of the ovum, 
which it quickly contracts, and renders slightly opaque. 
Besides those media which act chemically on the spermatozoa and the ova, I 
made trial, in this and the two following sets of experiments, with a solution of gum- 
arabic, the effect of which appears to be entirely mechanical ; and as the results are 
curious and seemingly important with reference to the nature of the agency of the 
spermatozoa in impregnation, I defer the mentioning of them until I have to show 
the effect of media which operate mechanically on the ovum or the spermatozoon in 
impregnation. 
The result of the preceding experiments was so remarkable, that it seemed necessary 
that they should be repeated with greater precision, with reference to exact periods 
2 G 2 
