THE Variation, races and migrations of the mackerel. 255 



grounds, to regard the Eamsgate autumn fish as anything but the 

 southern extension of the Lowestoft shoals. The Scilly data closely 

 resemble those from Brest in many respects, and the combined data 

 may be regarded as representing the mackerel off the mouth of the 

 Channel during June. 



Table IV., showing frequencies of values of Transverse Bars. 



(Percentages.) 



This table strikingly confirms the conclusions already drawn. The 

 resemblance between the percentage frequency of the different values 

 in the case of Plymouth and North Sea fish amounts practically to 

 identity, and the resemblance between the same data for Kinsale and 

 Kerry fish is almost equally exact. The combined Brest and Scilly 

 data also closely resemble the North Sea and Plymouth records. 



On the other hand, the American and the two Irish groups diverge 

 considerably from the others in the low percentage of the low values 

 and in the high percentage of the high values, and the American 

 sample shows this contrast still more markedly than the Irish groups. 



From the variation of this character, therefore, I conclude that the 

 mackerel examined fall into three groups, characterised by differences 

 in the frequency of high and low values of the transverse bars. These 

 groups, arranged in order of frequency of the high values, are : — 



1. American, in which 44% of the fish have 28 or more bars each. 



2. Irish, in which the number of fish having the same high 



number of bars varies between 34 % and 38 Vo- 



3. English Channel and North Sea (including Brest and Scilly), in 



which the number of fish having the high number of bars 

 varies between 20 % and 22 7o- 



I also conclude that these differences indicate a racial separation 

 between the three groups. The American fish are shown in the 

 sequel to be distinguishable from European fish in regard to every 

 character, .lO that I do not anticipate that my conclusion as to the 



