150 Symmetry of Egg and Symmetry of Embryo in the Frog 
II. The eggs were closely placed as above, but with their axes vertical, and 
their white poles below. Since the eggs did not have to turn over the possible 
influence of gravity is eliminated, but the pressure remains. 
III. While the eggs are placed as in T. with their axes horizontal, they are so 
spaced that their jellies do not touch. The pressure is eliminated, but gravity 
remains. 
IV. By placing the eggs wide apart and with their axes vertical both these 
possibly disturbing factors are removed. 
The direction of the incident light was also varied : — 
In I. the majority of the slides were placed and kept with one end to the 
window, but a few were kept in darkness until segmentation had begun. 
In II. the majority were placed with one end to the window, but in a few cases 
one side of the slide was directed towards the light. 
In III. one end of the slide was certainly directed towards the light in some 
cases, in the remainder I am not certain of the position although I believe it was 
the same. 
Lastly in IV". all the slides were placed with one end facing the light. 
The results of the measurements of the angles between the Plane of Symmetry, 
the First Furrow and the Sagittal Plane under the four main conditions (the 
possible effect of light will be considered later) are given in the accompanying 
Table VI. in which are entered the values of the standard deviations and 
correlation coefficients for each angle under each set of conditions. 
TABLES II.— V. 
Frequency of Angles between Plane of Syniinetry and Sagittal Plane. 
II. I 6 
III. f) 
IV. — 
V. — 
I ! i 
74 180 
98 173 
86, 48 
92 42 
41 i 14 
36 I 10 
9 12 
3 
4 [ 1 
1 3 
741 
792 
245 
245 
•54° 
±1-12 
-3-67° 
±•88 
2-73° 
±1-27 
•92° 
+ r36 
45 •29° 
±•79 
36 ^84° 
±•62 
29-37° 
±•89 
31 •50° 
Plane of Symmetry and Sagittal Plane ; the angle measured being between the "grey 
crescent" end of the former and the "dorsal lip" end of the latter. 
I]. Eggs close. Axes horizontal. 
III. Eggs close. Axes vertical. 
IV. Eggs spaced. Axes horizontal. 
V. Eggs spaced. Axes vertical. 
