THE VARIATION, RACES AND MIGRATIONS OF THE MACKEREL. 267 



Table YII., showing variation in Spottiness. 



This table brings out clearly (1) the decisive racial distinctness of 

 the American fisli, (2) the affinity between the fish from Brest and 

 Scilly with those of the Channel and North Sea, and (3) the racial 

 difference between the Irish fish and those of the preceding area. 



In general terms it may be said that the American fish are very 

 spotty, and the Irish fish, particularly off the west coast, are very 

 free from spots, while the fish which frequent the English Channel, 

 from its mouth to the coast of Norfolk, have a somewhat higher 

 percentage, both of spots and spotty fish, than those of the Irish 

 coast. 



That spottiness has no connexion with the size of fish examined 

 is clear from a comparison of the results with the table of sizes. 



The following figures prove the absence of any sexual peculiarities 



in the matter. They are based on the entire set of samples in which 



the sex of the fish was recorded, i.e., 100 American and 918 British 



fish. 



American fish. — Proportion of males to females . . .55:45) 



„ „ male to female spotty fish . . 59:41/ 



Deviation = 4 % 

 British fish. — Proportion of males to females . . .46:54) 



„ „ male to female spotty fish . , 44:56 J 



Deviation = 2 % 



IX. Number of Finrays in First Dorsal Fin. 



According to Giinther's Catalogue of Fishes (vol. ii., p. 357), the 

 number of finrays in the first dorsal fin of the common mackerel is 

 higher than in any other species of the genus Scomber, and varies from 

 11 to 14. The lowest number is presented by the Spanish mackerel 

 (S. colias), which is stated both by Giinther and Day {British Fishes, 

 i,, p. 91) to possess only 7 rays. An intermediate condition is shown 

 by S. pneumatophoriLS, which possesses 10 rays, according to the same 

 authorities. Steindachner, on the other hand, regards the two latter 

 forms as varieties of one and the same species, in which the number of 

 finrays would vary accordingly from 7 to 10. From an examination 

 of several specimens from the Mediterranean, which I owe to Professor 



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