282 
Proceedings of the Poyal Society of Edinburgh. [Sess. 
i. 
Total 
Numbers. 
ii. 
iii. 
iv. 
Total 
Numbers 
calculated. 
Number per Unit Area. 
Actual. 
Calculated. 
Centre circle . 
28 
28 
27-8 
27*8 
1st zone 
42 
14 
12-5 
37-5 
2nd „ 
28 
5*6 
5-8 
29-0 
3rd „ 
11 
1-57 
2*71 
19-0 
4th „ 
7 
•78 
1-26 
11-3 
5th „ 
7 
•63 
•58 
63 
6th 
5 
•40 
•274 
3*6 
7th „ 
4 
•26 
T28 
1*9 
8th ,, 
2 
T2 
•06 
1*0 
9th „ 
1 
•05 
•028 
•53 
The dispersion of Daphnia may also be compared with the formula 
_r 
y = ae & by summing parallel to one axis. A comparison is given below 
when the Daphnise were so counted. The numbers are as follows : — 
Actual. 
Theoretical. 
2 
1-9 
7 
9-4 
46 
39-5 
35 
39-5 
11 
9-4 
1 
T9 
giving x 2 = 2'34 or P = *75. 
Cyclops. 
Cyclops were used in a few experiments but found very unsatisfactory. 
Not only did they photograph with great difficulty on account of their 
transparency, but they moved on dispersal strongly towards the light. 
A sectional count of one instance is given (Diagram V.). It is not 
treated as a whole, but it is to be noticed that the advancing edge is very 
closely given by the exponential curve which has been fitted to it. 
The values are : — 
Actual. Calculated. 
33 35 3 
20 19-2 
12 10*7 
7 5-9 
5 33 
2 1-8 
which gives x 2 = P61 or P = ’9, so that the fit is very close. 
