280 Proceedings of the Royal Society of Edinburgh. [Sess. 
In several instances the Daphnise, instead of grouping themselves along 
one edge of the dish, arranged themselves as if one corner of the dish were 
the centre of attraction. From this point outwards in all directions of the 
quadrant their numbers diminished. This, however, was observed only 
once, when the light was good enough for instantaneous photography. To 
OMGGfW IF 
20 
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D/JP/J/V//7 (6) 
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count the numbers of the organism, concentric circles were drawn on 
the plate and the organisms between each pair of concentric circles 
in the quadrant counted. Some difficulty was experienced, however, 
at the greater distances, as in places it seemed that the outlyers of 
other groupings were even invading the periphery of this. All the 
organisms were counted, however, and none rejected. The figures are given 
in the following table : — 
i. 
Total 
Numbers. 
ii. 
iii. 
iv. 
Calculated 
Total. 
Number per Unit Area. 
Actual. 
Calculated. 
Centre quadrant 
19 
19 
18-4 
18-4 
1st 
„ zone 
33 
11 
11T 
33 3 
2nd 
?? n • 
37 
7-4 
6-78 
339 
3rd 
5? 
18 
2-67 
4T6 
29T2 
4th 
5 ? V • 
24 
2*67 
2-55 
22-95 
5th 
5) 5? 
19 
1*72 
1-57 
16-27 
6th 
)) 5? 
17 
1-31 
•96 
12 r 5 
7th 
'A 5? 
11 
•73 
•59 
8*9 
178 
46-50 
46T1 
177-14 
It is easier to examine this grouping when the numbers are reduced to 
the population per unit area. On the hypothesis the grouping should be 
