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question is only of individuals 1 — 2 — 3 — 4 — 5 years old, I suppose we need 

 not pay an}' regard to this, as we must with respect to the forest, with trees which 

 are often 100 years old and which must have substitutes for all the 99 years ; 

 and particularly so, as the plaice of various annual series frequent various 

 parts of the seas, and generally do not mingle with one another; therefore 

 they will scarcely take up the room for one another to any very great extent. 

 I have wanted only to mention this as a formal possibility, which cannot 

 be passed over by the theoretical discussion of this whole matter. It would 

 be otherwise perhaps, in seas where too much protection was to be feared, 

 but it will scarcely be necessary to enter more closely into this side of the 

 question. 



This view of the cause of the decreasing flat-fishfisheries in our seas 

 is here set forth for the first time with more thorough proofs ; no one, as 

 far as I know, has published opinions which quite agree with mine. 



In Scotland has Dr. Fulton supposed that it would be sufficient if we 

 took care that the fish were not caught till they had spawned once., as 

 they would then have contributed to the continuation of the species; and 

 E. W. L. Holt, in England, has also thought of augmenting the profit of the 

 fishery by artificial fecundation of the eggs, perhaps in connection with hatching 

 by artificial means. Also other ways have been proposed in order to im- 

 prove the fishery (prohibitions against fishing that destroys the quite small 

 flat-fish, regulations with regard to the width of the meshes, etc., into which 

 I shall enter more closely in the next chapter), but it seems to me that 

 this has been done almost always with the secret thought that it is the 

 propagation, the increase of the number of individuals which is the principal 

 thing in the whole question. Cunningham, however, has incidentally set 

 forth the thought (in contradistinction to Dr. Fulton) that it is of greater 

 moment that a fish is grown-up than just sexually ripe, particularly if it 

 becomes ripe when j r oung and with a small size; but he looks upon 

 this as a thing impracticable on deep water as far as the trawl is concerned. 

 (J. Mar. Biol. Ass. (N. S.) II, p. 116). It will be perceived that I lay the 

 greatest stress on the growth of the single individuals. My theory might be 

 caUed therefore the growth-theory in contradistinction to the other propaga- 

 tion-theory. 



It has always been hard for me to believe that there should be any want 

 of eggs of plaice in our seas, partly because Hensen's excellent investigations 

 have shown what immense quantities there are of them, partly because I 

 myself see our seas filled up with such eggs. 



