Raymond Pearl and Wilbur N. Fuller 
217 
The values for the mean, standard deviation (with Sheppard's correction), and 
coefficient of variation deduced from this frequency distribution are as follows : 
Mean = 142-715 + -362 somites. 
Standard Deviation = 11 '850 + '256 somites. 
Coefficient of Variation = 8-303 ± -181 %. 
Fig. 1. Variation in number of Somites in body of Earthworm. 
55 
60 
45 
40 
35 
30 
g 
h 25 
20 
15 
10 
5 
in 
79 85 90 95 loo 105 110 115 120 125 130 135 140 145 150 155 160 164 
Number of Somites. 
Turning to the character " length of body " we have the frequency distribution 
given in Table II. 
TABLE II. 
Length of Worms. Glass unit = 2 5 cms. 
Length in 
centimetres 
Frequency 
10 —12-5 
7 
12-5—15 
50 
15 —17-5 
75 
17-5—20 
153 
20 —22-5 
137 
22-5-25 
55 
25 -27-5 
9 
27-5—30 
1 
Total 
487 
Biornetrika ly 
28 
