J. W. Jenkinson 
171 
TABLE XXV. 
First Furrow atid Plane of Symmetry. 
^ Totals 0 
2 : !• 
1 
Totals 
37 
42-74°. 
p = -641 ±-051 or when the 90° is not halved = -736 ± -037. 
other hand there is, even under the most unfavourable circumstances, some coiTcla- 
tion between the First Furrow and the Sagittal Plane, while under the influence of 
pressure alone the correlation is very fair. 
This is a point to which we shall return when we have discussed the internal 
causes which fix the positions of the Plane of Symmetry and the Fii'st Furrow. 
PART II. 
As will be well remembered, it has been asserted by Roux that the position of 
the First Furrow of the Frog's egg depends upon the point of entrance of the 
spermatozoon. Roux found either (1) that the sperm-path (the track of pigment 
left behind it in the egg by the entering spermatozoon) was either included in, or 
close to and parallel to the First Furrow, or (2) that if the path was iuclined at 
an angle to the Furrow there was an inner portion which lay parallel to, or was 
included in it. The path was found to be in or parallel to the Furrow when the 
eggs had their axes vertical from the beginning, to be inclined to it when the eggs 
were (permanently) prevented from assuming their normal position. In the second 
the outer inclined portion was distinguished as the ' penetration ' path, the direction 
of first entrance of the spermatozoon, from the inner parallel portion, or 'copulation' 
path, the line, that is, of union of the two pronuclei. In the first case the two 
portions were regarded as lying in one and the same meridian, since the ' penetra- 
tion ' path is directed towards some point in the axis, and the ' copulation ' path 
22—2 
