Variation in Portunus depurator. 229 



K 4. L. Antero-lafceral. 1432 Individuals (see fig. 2). 



The critical function 2ft 3^6 = O306116 is positive, and so the 

 range is unlimited, as was the case with the total and frontal 

 breadths. 



Using Professor Pearson's skew curve of unlimited range, and 

 putting 



x = a tan 0, 



we have y = y cos Zn Ocr* 9 , 



where y = 152-4817. v = 4-550107. 



m = 22-123325. a = 19-291468. 



The distance of axis y from centroid = 2'077756, and the distance 

 of maximum ordinate from centroid = 0'093918. Both, this and the 

 normal curve are drawn, and there is but very little difference 

 between them, the areal deviations being 7*5 and 7'9 per cent, 

 respectively. 



B. Dentary Margin. The mean has a range of about 3 units, and 

 it rises as the crab grows. The total range of deviation = 436 539 

 thousandths. As in the other cases, groups 6 12 were selected, and 

 a frequency curve drawn ; the range is 436 531 thousandths, giving 

 24 units. 



