APPARENTLY CORRELATED TO THE CONDITIONS OF LIFE. 
319 
Tables Showing Vakiations in the Average Katio of Length to LpvEadtji 
IN Shells from Different Localities. 
Explanation .—In tlie first column of these Tallies the actual measurements of the 
lengths and breadths of each shell are given in millimetres. The second column is 
constructed from the first. It shows the number of shells of each length which 
compose the sample of 30, and also shows the average breadth of shells having the 
same length. The third column is constructed from the second by dividing the 
average breadths in each case by the length. The final average ratio is obtained 
from the third column by multiplying these cjuantities by the number of shells from 
which they were derived, adding together these products and dividing the sum by 30. 
[In the column in which the breadths are given the figures in brackets show the 
number of shells having the same breadth.] 
Table I.—The Aral Sea . 
Measurements of shells in millimetres. 
Average breadth of shells having 
the same length. 
Length. 
Breadth. 
Length, 
Average 
breadth. 
Number of 
shells. 
Ratio of length to 
breadth. 
22 
17-5, 17(L 
22 
17T 
5 
1 :0 77 
21-5 
16 
21-5 
16 
1 
*74 
21 
160) 
21 
16 
4 
75 
20-5 
16 
20-5 
16 
1 
76 
20 
16-5,160), 15-50), 150)A4 
20 
15-4 
13 
77 
19-5 
15-5, 15, 14 
19-5 
15 
1 
•76 
18-5 
14, 13 
19 
14-8 
3 
76 
' 
18-5 
13-5 
2 
72 
Average ratio of length to breadth in 30 shells varying in length between 22 mm. and 18'5 mni. 
is 1:0761. 
