154 Symmetry of Egg and Symmetry of Embryo in the Frog 
Plane of Symmetry and Sagittal Plane. 
90 — O + 90 
CO 
e 
c 
s 
90 
Fig. 4. Eegression Scheme constructed from Table 111. The dots mark mean values 
of the angle between Plane of Symmetry and First Furrow. 
Ill short, between the first furrow and the sagittal plane in the frog's egg there 
is no correlation, or — if the correlation table is an expression of that canon of 
induction known as the method of concomitant variations — no causal connection. 
The two planes coincide in so many cases merely because each, as we shall see, 
and particularly the sagittal plane, tends to lie in the plane of symmetry. Beyond 
that there is no connection between them. The symmetry of segmentation and 
the symmetry of the embryo are independent, and in this case at least the truth 
of Driesch's famous aphorism is vindicated — " Furchungsmosaik braucht kein 
Mosaik der Potenzen zu sein." 
II. Plane of Symmetry and Sagittal Plane. 
■ The number of observations is here not so great, but still great enough to 
produce a symmetrical result (Table IV., Fig. 5). It will be seen that the 
tendency of these two planes to coincide is more considerable, the standard 
deviation being smaller than in the case of the first furrow and the sagittal plane. 
TABLE IV. Plane of Syiyimetry and Sagittal Plane. 
Groups of 10°. 
Class 
Frequency 
Class 
Frequency 
90—81 
4 
+ 0—10 
91 
80—71 
6 
11—20 
52 
70—61 
3 
21—30 
42 
60—51 
8 
31—40 
27 
50—41 
14 
41—50 
15 
40—31 
23 
51—60 
7 
30—21 
29 
61—70 
11 
20—11 
60 
71—80 
6 
10-0 
103 
81—90 
8 
509 
M= 2 -23° ±-889 
o- =29-75°+ -629. 
