J. W. Jenkinson 
167 
The range of 7 in series B is equal to the range of 7 in series III. and IV. 
(Table XII.) : in A it is rather wider. 
In all three (positive) series the mean value of a(= /3) when 7 = 0 is about the 
same. The least mean values of a and /3 compatible with /3 and a being positive 
(or ^ positive and a negative in the negative series) are about the same except 
in A, negative series, where that of ^ is less than that of a. 
In the positive series y8 changes faster than a as 7 alters. 
In Ba, /3 will be more often less than a than in B ^8. 
The variability of when 7 is constant is always less than that of 7 when ^ is 
constant (compare Table XIII. IV.), but, unexpectedly, ^ has a greater variability 
than a (except in A, negative series), a has always a less variability than 7. 
It appears indeed that in this series of experiments, when the constants are 
calculated by Pearson's method, the relation between Plane of Symmetry and 
Sagittal Plane is not as close as one would have anticipated (compare the values 
of p^y in Tables XVIII. and XI. IV., and of in Tables XVII. and VI. IV.). 
There certainly are more instances of angles over 90° than were found in the 
series given in Table V. 
Lastly, we have to consider the position of each of these planes separately with 
regard to the direction of the incident light (Tables XXI. — XXIII.). 
From Table XXI., which gives the position of the First Furrow, it is clear 
that this plane is not affected by light. It may occupy any position, and the 
TABLE XXI. 
First Furrow. 
Angle 
A. Light 
(from -90°) 
B. Darkness 
- 90—75 
75—60 
60— 43 
45—30 
30—15 
15—0 
+ 0—15 
15—30 
30—45 
45—60 
60—75 
75-00 
22 
13 
18 
18 
23 
11 
14 
21 
16 
11 
17 
16 
56 
68 
55 
57 
53 
59 
57 
48 
45 
54 
53 
54 
Totals 
200 
659 
M 
-3-45° ±2-49 
-2-75° ±1-38 
cr 
52-17°±l-05 
52-55° ±-98 
