J. W. Jp^NKINSON 
157 
In whatever way we compare the relations between Plane of Symmetry, First 
Furrow and Sagittal Plane, whether by the standard deviation (first method), the 
correlation coefficient (first or second method), by comparing the mean values of 
two when the third is known, or by comparing the variabilities, it seems clear that 
there is a closer relation between the Plane of Symmetry and the Sagittal Plane 
than between either of these and the First Furrow, at least when the disturbing 
effects of either gravity or pressure are removed. 
Let us consider now the relation between each of these planes and the direction 
of pressure, of the gravitation symmetry plane (including the egg-axis and the 
vertical) and of the light. These relations are immediately obtainable from the 
observed values of the angles between the planes and the lines ruled across the 
slides. It is only necessary to remember that in all cases the pressure is from 90° 
to 90°, the gravitation plane from 0° to ]80°, the white pole of the egg being 
towards 0°. The direction of the light, as already mentioned, differs in the several 
experiments, and will be noted in each. 
A. Let us take first the position of the First Furrow (Table XIV. and Fig. 1). 
TABLE XIV. 
First Furrow. 
I. 
II. 
III. 
IV. 
Eggs close 
Eggs close 
Eggs 
spaced 
Eggs spaced 
Axes horizontal 
Axes vertical 
Axes horizontal 
Axes vertical 
Angle 
A 
B 
A 
B 
A 
B 
All cases 
Darkness 
All cases 
Light from 
All cases 
Light from 
Light from 
0° 
+ 90° 
+ 90° 
- 0—15 
2.3 
2 
58 
4 
18 
6 
40 
15-30 
23 
2 
57 
5 
14 
2 
37 
30— 4,5 
19 
2 
81 
6 
29 
36 
45— 60 
50 
76 
7 
23 
4 
43 
60—75 
88 
95 
15 
24 
13 
40 
75—90 
114 
2 
133 
27 
23 
14 
34 
+ 90—75 
102 
2 
148 
31 
29 
29 
75—60 
112 
8 
90 
15 
31 
10 
34 
60— 45 
4 
62 
22 
6 
29 
45—30 
4.5 
3 
58 
5 
22 
27 
30—15 
26 
1 
56 
11 
25 
6 
15-0 
28 
2 
81 
12 
23 
8 
43 
Totals 
687 
995 
283 
419 
M 
3-92° ±-97 
•12° 
f99 
3-36' ±1-98 
3-81° ±1-65 
(T 
38-16° ±-69 
46-47 
±■71 
49-32° 
±1-40 
52-76°±l-17 
The direction of pressure is from 90° to 90°. The gravitation symmetrj' plane is at 0°. 
