﻿Even though we may point out other peculiarities than difference in 

 size in the plaice from different parts, for instance a somewhat different 

 number of rays in the fins, etc., this does not prove neither that we have 

 to do with real races, which propagate generation after generation with the 

 peculiar stamp of the race; for we must prove first that these peculiarities 

 have not, like the size, been produced by the natural conditions for each 

 single individual in the first generation. It lies pretty near, certainly, to 

 think that it is so with the plaice, also, for instance, with regard to the 

 variation in the number of rays in its fins; for its pelagic eggs and fry 

 are by the currents carried about in nearly all our more open seas so 

 quickly that a close intermixture of the eggs of all plaice must seem to be 

 the unavoidable result. When, in spite of this intermixture of eggs and 

 fry, the plaice after all appears in one »/ora« in the Belts (and the Baltic) 

 and in another »form* in the Cattegat properly so called, forms which are 

 not intermixed, then this may be the result of two circumstances: 1) that 

 eggs or fry of one form die when they are carried into the territory of the 

 other; 2) that eggs and fry of one form, when they are carried into the 

 territory of the other live, but, by the natural conditions there, are developed 

 into fish of the »form « which belongs to that place, though their parents are of 

 the other »form«. — We might suppose, for instance, that eggs and fry of 

 the larger form are unable to live in as brackish water as the fry and eggs 

 of the smaller form, and that they must die, therefore, if they are carried too 

 far up our seas; but it is scarcely probable that eggs aud fry belonging to 

 the form that lives in brackish water should die also, when carried into 

 water of greater salinity; for if the eggs can stand the brackish water then 

 they will live so much the better in the salt water, where most eggs of 

 plaice are to be found. The first supposition alone 1) will then scarcely 

 be able to explain the geographical separation of the two forms, and I be- 

 lieve that the second supposition, that one »form« changes into the other 

 already in the first generation, is necessary. 



I hope some day to return to this interesting question, and to give 

 further information on it than I am able to give at present. The question is 

 one of the greatest interest, both theoretically and practically, as it touches 

 on the formation of races as this is actually going on in nature, as also on 

 the other question: whether it may be possible to improve on our races of 

 little plaice by the introduction of larger races, which not only grow to a 

 larger size but also grow quicker and consequently give a greater profit of 

 the whole stock of fish. 



