160 Symmetry of Egg and Syninietry of Embryo in the Frog 
A comparison again of the frequencies in columns II. B and III. B, in the first of 
which the light is from 0°, in the second from 90°, shows that there is no greater 
tendency for the Furrow to lie either in or at right angles to the source of light in 
the one case than in the other. 
We conclude, therefore, that light plays no appreciable part in determining the 
position of the First Furrow in the egg. 
B. It is very different in the case of the Plane of Symmetry. In Table XV. 
are given the frequencies of the various values of the angle between the Plane of 
TABLE XV. Plane of Symmetry. 
I. 
II. 
III. 
IV. 
Eggs close 
Eggs 
close 
Eggs spaced 
Eggs spaced 
Axes horizontal 
Axes vertical 
Axes horisjontiil 
Augle 
A 
B 
A 
B 
A 
B 
Light from 
Darkness 
Light from 
Light from 
Light ? 
Light from 
Light from 
+ 'J0° 
+ 90'^ 
0'" 
+ 90° 
+ 90° 
_ igQ 7(;5 
10 
1 
51 
9 
6 
4 
20 
165—150 
7 
0 
48 
10 
1 
5 
15 
150—135 
6 
1 
31 
2 
3 
6 
8 
135 — ISO 
18 
1 
49 
G 
2 
2 
13 
120—105 
24 
0 
21 
G 
4 
6 
16 
105—90 
34 
4 
41 
6 
8 
1 
12 
QQ '^g 
58 
4 
63 
11 
10 
5 
19 
75—60 
32 
6 
20 
4 
8 
3 
9 
60—1(5 
30 
6 
22 
3 
9 
5 
4 
J^—30 
56 
8 
23 
4 
15 
3 
7 
30—15 
40 
8 
21 
8 
8 
3 
7 
15—0 
47 
21 
39 
12 
21 
4 
12 
+ 0-15 
40 
12 
31 
12 
3 
18 
15—30 
29 
13 
18 
4 
20 
5 
7 
30—1(5 
17 
!J 
23 
3 
8 
4 
6 
45—60 
3 
11 
1 
G 
2 
6 
60—75 
27 
4 
5 
3 
8 
2 
4 
75—90 
36 
17 
15 
9 
1 
2 
90—105 
22 
6 
15 
7 
6 
5 
6 
105—120 
14 
3 
11 
8 
7 
8 
120—135 
7 
0 
21 
2 
2 
5 
9 
135—150 
28 
0 
20 
4 
8 
4 
18 
150—165 
22 
0 
51 
11 
3 
12 
165—180 
21 
0 
71 
16 
7 
3 
22 
Total 
115 
M 
-■59° ±1-81 
0" 
*28-65°±r27 
The direction of pressure is from 90° to 90°. The gi'avitation symmetry plane from 0° to 180°, 
the white pole being turned towards 0°. 
* Calculated on groups of 30°. 
