318 PECULIARITIES OF PLAICE FROM DIFFERENT FISHING GROUNDS. 



500 mm. in length, so that -01 of the total length varied from 2 mm. 

 to 5 mm., but -001 would have implied accuracy to from -2 to '5 mm., 

 which was greater than the accuracy of direct measurement. (Con- 

 sidering the great variations in the proportions with age and condition 

 of the individual, differences between local races not exhibited in 

 hundredths of the total length may be regarded as quite unimportant. 



The direct results of the examination of the specimens and calcula- 

 tion of percentages are recorded in Tables A appended to this paper. 

 The sexes are recorded separately, and the specimens given in order 

 of total length, in order to show what variations depend upon sex or 

 increase in size. 



The comparison between the samples from different localities, in 

 Tables B, has been made by placing side by side the actual numbers 

 of individuals observed to have each degree of variation which was 

 distinguished. Duncker has given tables of frequency, but they differ 

 from mine in two respects; firstly, that he takes the larger stages of 

 variation mentioned above, and secondly, that he has given the i^er- 

 centafje of individuals, not the actual number. As the number of 

 individuals was in my investigation rather small, and as the object was 

 only to ascertain and compare the distribution of the variations, no 

 advantage appeared to be gained by comparing the percentages of 

 individuals instead of the actual numbers. 



The largest number of individuals have been examined in the case 

 of the Brown Eidges and the Norfolk coast, these being the two 

 principal distinct regions where the sailing trawlers of Lowestoft 

 work. From the other two regions, namely, the Eddystone grounds 

 and the ground to the north-east of the Dogger Bank, a smaller number 

 were obtained. All those from the Brown Bidges were examined at 

 Lowestoft, and also the greater number of those from off the Norfolk 

 coast: the latter include samples taken outside the Dowsing Bank, 

 off Cromer, and off the Well Bank. An additional sample, taken 

 fourteen miles from Cromer, was sent to me in London from Lowestoft, 

 The Plymouth samples were sent from the Plymouth Laboratory. The 

 remaining sample was a box sent from Billingsgate, and stated by 

 the sender to have been caught 220 miles from Smith's Knoll, just 

 to the north of the tail of the Dogger Bank, at a depth of 25 fathoms. 



I will proceed now to the comparison of the various characters in the 

 samples. 



According to the statistical enquiries of Mr. Francis Galton and 

 Professor Weldon the magnitude of a character which occurs with 

 the greatest frequency nearly coincides with the arithmetical mean 

 of all the observed magnitudes, and the frequencies of the other 

 magnitudes are symmetrically disposed about the maximum frequency. 



