240 
MR. NEWPORT ON THE IMPREGNATION OF 
the abdominal muscles and the motions of the viscera, and not necessarily through 
the aid of the male during copulation. Second, changes are going on in the consti- 
tuents of the egg, both before and after oviposition as well in the unimpregnated as 
in the impregnated condition ; but they soon cease in the former, and do not pro- 
ceed to the cleaving or segmentation of the yelk. Third, that the egg is not sus- 
ceptible of impregnation until after it has acquired the envelopes which it gains in 
the oviduct. Fourth, that endosmosis of the entire egg takes place through these 
envelopes, and is most rapid during the few minutes the egg is most susceptible of 
impregnation. Further, that this endosmosis is augmented and hastened by an in- 
crease, and is lessened and retarded by a diminution of temperature ; and that the sus- 
ceptibility of the egg to become impregnated, and produce, is in exactly the same con- 
dition with regard to heat ; whether the egg be exposed to, or whether it be excluded 
from light. Fifth, that only extremely minute granules of solid matter can by any 
possibility pass into the tissue of the envelopes during endosmosis ; and that there 
is no evidence whatever of the existence of a fissure or orifice, in the envelopes of the 
egg of the Amphibia, at the time of, or before impregnation, capable of admitting 
the spermatozoon to the interior of the yelk-membrane or its contents. Sixth, that 
it is the spermatozoon alone which effects impregnation ; and that this does not take 
place until the spermatozoon is brought into immediate contact with the external 
envelopes of the ovum. Seventh, that the liquor seminis, when entirely separated 
from spermatozoa, certainly does not effect impregnation. Eighth, that although 
direct contact of the spermatozoa with the ovum is indispensable to effect impreg- 
nation, I have never been able to detect any traces of these bodies in contact with 
the yelk-mernbrane, or even within the substance of the external envelope. Ninth, 
that impregnation is commenced the instant the spermatozoa are brought into contact 
with the egg, but a certain duration of contact is essential to its completion. Tenth, 
that impregnation is not effected when the whole or the majority of the spermatozoa 
in contact with the envelopes have previously become motionless and, apparently, 
have lost vitality, as they are found to have done after the lapse of a longer or shorter 
period. Eleventh, that although an exceedingly minute quantity of spermatozoa suffice 
to impregnate the ovum, the phenomenon of impregnation takes place more tardily, 
even with duration of contact when the number is extremely limited, than when it is 
in full abundance, without excess ; while when the quantity is deficient, or the dura- 
tion of contact too limited, then the phenomenon is incomplete, and partial impreg- 
nation only is effected. Twelfth, partial impregnation is shown in imperfect segmen- 
tation of the yelk ; and is due chiefly to the spermatozoa being insufficient in quantity, 
or in duration of contact, or inefficient through diminished vitality ; and it may also 
result from diminished susceptibility in the ovum. Thirteenth, partial impregnation 
of the ovum is of frequent occurrence, as I found in my first experiments with fluid 
that had passed through filtering-paper, but which still contained a very few sperma- 
tozoa, either motionless or exceedingly feeble ; and further, partial impregnation is of 
