210 
MR. NEWPORT ON THE IMPREGNATION OF 
noticed this in other ova, I was inclined to attribute to some normal change in the 
yelk itself, perhaps of an imbibing or endosmic character. 
No. 2. One hundred and ninety-seven ova were shed into water mixed with the 
remaining portion of fluid which had passed through the four filters, but not a single 
egg gave even a trace of segmentation. Many of the yelks had the same peculiarly 
irregular outline as in No. 1. These two experiments I regarded as a satisfactory 
proof that it is not the fluid portion of the semen which impregnates. 
No. 3. Two hundred and four ova were passed into water upon the third filter, 
already immersed in it, and the fluid on which showed an oceasional spermatozoon. 
I was unable to detect any impregnated ova in this experiment, but, as the result 
showed, a few had been affected, as four embryos were produced. 
No. 4. Three hundred and seventy-one ova were passed into water upon the first 
or topmost of the four filters, and which had already been placed in the water. At 
four hours and thirty minutes^ almost every yelk had become segmented. The ehange 
had occurred some length of time before this, as the second or crucial segmentation 
was commenced. This experiment seemed to be a most direct and conclusive proof 
of the agency of the spermatozoa. At the end of four days almost the whole of the 
eggs were producing embryos, many of which were advanced to the fourth period of 
development. One hundred and twenty-seven became fully formed and vigorous, 
besides nearly as many more which did not complete their changes, from an accidental 
cause. 
Before these concluding experiments were made, I had already, in March last, 
repeated the preceding; but, as the filtration was less perfect, have thought it un- 
necessary to give them in detail ; they agreed however in the results. The whole 
have confirmed in the fullest manner the experiments first made, and have proved, 
as I trust, satisfactorily that the spermatozoa alone are those parts of the semen 
which effect the impregnation of the ovum. Having repeated the filtration in five 
separate sets of experiments, on different occasions, and with exactly the same gene- 
ral results, I can no longer entertain any doubt of the direct agency of the sperma- 
tozoa. The conclusion, I think, is rendered certain by facts now shown, which escaped 
tlie notice of Spallanzani, and of Prevost and Dumas. Segmentation of the yelk 
takes place earlier when impregnation is effected by a large, than when occasioned by 
a very small number of spermatozoa, the temperature of the surrounding medium, and 
all other circumstances, being alike in the two cases, as in the experiments Set A as 
compared with B (p. 190). This fact is supported by another, equally significant. 
When only a very small number of spermatozoa exist in the fluid, then the remarkable 
result of partial impregnation often takes place, and the ova are unproductive. On 
the other hand, when spermatozoa are supplied in full abundance to the ova, not 
only does segmentation of the yelks take place more rapidly, but also more exten- 
sively, and almost every ovum produces an embryo. 
With regard to the liquor seminis, it seems equally decisive that this portion of 
