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younger than 1 year, the 1-group all fish between 1 and 2 years, and the 

 2-group all between 2 and 3 years; each of these groups is consequently in 

 .the main an annual series which, however, is often closely connected with 

 the preceding and following annual series. The 3-group, on the other hand, 

 does not only represent the fish between 3 and 4 years, but on the tvhole all 

 specimens over. 3 years. We might expect that this last mentioned group would 

 contain an overwhelming number of specimens, but it does not seem to be 

 so. As it has also "always been supposed, the mortality of the tender fry 

 (not to mention the eggs) must be great, and though it is difficult to avoid 

 mistakes in making an estimate of the number, based on our enumerations, 

 I do think I can perceive a decrease in number, for instance in the young- 

 plaice from their 1st to then 2nd and 3rd year, so that, for instance, the 

 1-group contains fewer specimens than the 0-group. But the reason of this 

 might be that it is easier to catch the little fish, because they keep together 

 on shallow water, so I shall not enter further into this question. — 



While the groups 0, 1 & 2 are changed in size in the course of the 

 year, the upper part of the 3-group will always be confined by a more or 

 less constant curve. The lower part of the 3-group, on the other hand, is 

 much changed because it is amalgamated with the 2-group at a certain time 

 of the year. A line, where this amalgamation takes place, will be perceived 

 at about 10 inches on the table. All specimens above this line may be called 

 mature and grown-up, i. e. the specimens of the species longer than this have 

 generally spawned once, or are just going to spawn, and they do not now 

 grow so quickly that we can distinguish between the various annual series. 

 The single individuals, however, may still grow, though perhaps but few of 

 them do so, and only quite gigantic specimens reach 14 — 14y 3 inches. — 



When we examine the size-groups of some species of fish in a certain 

 sea, we will often find only one or two annual series there represented ; the 

 youngest annual series (the 0-group of the plaice is for instance quite miss- 

 ing in the parts of the Baltic Sea which we have explored (see table VII & 

 VIII); the 1-group and, particularly, the 2-group are on the other hand 

 abundantly represented; the 3-group is so scarce that we are compelled to 

 believe in an emigration from the Baltic Sea of its specimens. 



Something like this is the case also with Pleur. limanda (see table XI). 

 Its 0-group is missing, as far as we know, in the Baltic Sea east of Falster 

 and Sealand, and its 3-group is there exceedingly rare. The table shows 

 also that the 3-group is not to be found everywhere in the Cattegat, while 

 it is very numerous at certain places (column 1). 



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