AND THEIR DISTRIBUTION AT DIFFERENT AGES. 



97 



species included in this paper are trawl-fislies. Each, table is followed 

 by a short commentary, and at the end of the paper I have 

 summarised and compared together the results brought out by the 

 tables. 



Pleuronectes flesus, the Flounder. Specimens reared in the 



Aquarium, 



The above table gives the growth actually observed in a large 

 number of specimens kept in captivity and abundantly supplied with 

 food. The most striking feature of the result is the very great 

 variation in growth among these individuals, spawned at the same 

 season, and therefore not differing by more than a few weeks in age. 

 Whether there is as much variation under natural conditions is a 

 question that immediately suggests itself. It is evident there is 

 considerable variation in the rate of growth in nature, from the 

 difficulty of distinguishing in a large number of fish those of one 

 year's, two years', and three years' growth. It is not difficult to 

 recognise with certainty young fish only a few weeks or months old ; 

 but the individuals of a given species brought up in numbers at a 

 single haul of the great beam-trawl form usually a regular series of 

 sizes, so that it is difficult if not impossible to separate definitely 

 those which are one year old from those which are two, and those 

 which are two years from those which are three. 



Another point of interest is the relation of age to sexual maturity. 

 According to Dr. Fulton's investigations, the smallest ripe flounder 

 is 7 inches long. Nov/ some, namely two out of fifty-one speci- 

 mens, of my captive flounders had reached and passed this limit 



