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MR. NEWPORT ON THE IMPREGNATION OF THE OVUM, AND 
On the 'production of the Body and Head of the Embryo from definite portions of 
the Yelk. 
Repeated observations have demonstrated that in one part of the yelk the head, and 
in another the body and tail of the forthcoming- being- begin. This appointment of 
the parts is further indicated, very early, by conditions in the yelk cleavage — condi- 
tions so constant that 1 am able to predicate soon after the completion of the hori- 
zontal cleft, or at the beginning of the fourth change, where the head, and where the 
tail of the future embryo will be placed. In support of this statement the changes 
in the egg undergoing segmentation must be referred to, but they will be traced, 
here, only to the point indicatory of the diagnosis to be made. 
To ascertain the correctness of the following statement it will be necessary to put 
the impregnated eggs, dark surface uppermost, in tube- cells, and to mark on these 
where the future head and body should be, according to the deduction from changes 
in the segmenting yelk. 
First change. — In eggs kept at a temperature of 60° Fahr., the first change begins 
at about the end of four hours, and consists in a cleft that runs vertically round the 
egg. This cleft may be called axial from its position, as it will afterwards appear, to 
the body of the future embryo. It begins in the centre of the dark surface in a 
slight depression, so that in some instances the canal may be almost detected : then 
suddenly a sulcus appears on each side of the depression, and quickly extends out- 
wards around the yelk, though it is deepest and most strongly marked above. In 
the egg of the Frog as in that of the Newt, the halves are not always of equal size in 
this stage, but this disproportion is obviated in the second division. 
Second change. — Another cleft now surrounds the egg crossing the first at right 
angles, and this may be named crucial. An interval of about an hour elapses before 
its appearance, and its commencement is not seen at the same instant on each side of 
the axial line, but is perceived first at one side. After this, as after the axial cleft, 
the pieces into which it divides the yelk are unequal in size ; but these variations 
have in general but little influence on the result obtained by the segmentation. 
In some ova there is such an unusual displacement of the segments as almost to 
prevent the identification of the parts in the subsequent changes, the lines of the axial 
and crucial clefts being rendered very irregular by unequal increase of the sectional 
pieces on opposite sides of the first cleft. This irregularity I am inclined to think 
arises from unequal division of the yelk in the production of the first cleft ; and to it 
I attribute the partial horizontal movement of the yelk itself, which may be some- 
times recognized. 
But when the yelk has divided with perfect equality both axially and crucially, the 
pieces on one side of the crucial line (in front say) always become larger than those 
on the other side (behind) ; and during this increase in size the anterior divisions 
project backwards over the posterior so as to cause a bending of the crucial sulcus, 
the convexity being forwards. 
