380 THE FLOUNDER FAMILY. 



be at least 3^ months old and the largest are probably 8 or 

 9 months. Dabs and lemon-dabs of six inches or therea.bout 

 may be put down as having attained the age of two years. 

 As regards later growth Dr Fulton has conducted a series of 

 experiments upon young dabs confined in a tank. One specimen 

 (8§ inch) grew 2^ inches in length and increased from 4 oz. to 

 IO5OZ. in weight in 16 months: another (7^ inch long) grew 1| 

 inches and more than doubled its weight : yet another (10| 

 inches) grew to 12^ inches in length in the same period of 

 time and increased in weight from 8 oz. to 14J oz. Young 

 plaice under exactly the same conditions showed a far slower 

 rate of growth both in weight and size. 



The smallest of the above dabs spawned when 10 inches 

 lono-, but apparently not till then, so that it appears that the dab 

 occasionally does not become sexually mature till the third year. 



Cunningham has made similar experiments with dabs under 

 domestication in Plymouth Laboratory. On capture in Sep- 

 tember and October, 1891, they were from 1| to 2| inch, and 

 by March, 1892, they were from 2 to 4| inches. A year after- 

 wards, at which time less than half of them survived, the 

 remainder measured from 4;^ to 8J inches. 



Sundevall' considered that the dab took four or five years to 

 attain its ordinary size of from 20 to 2.5 cm. (9 — 10 inches). 

 He took specimens from 34 to 133 mm. on the 19th May, and 

 thought that the first was a year old ; that of 94 mm. a year 

 older ; both it and specimens 133 mm. long being in their third 

 year. 



The Flounder. (Fleuronectes flesus, L.) 



Although a much smaller fish than the plaice the flounder 

 is a very near ally, and so resembles it in structure that a 

 casual observer might conclude that the life-histories of the 

 two were closely similar. It is a point especially fraught with 

 interest to find therefore that all the known facts in relation 

 to the two species tend to emphasize the conclusion that they 

 are widely separated in their habits and their migrations — as 



' Siunid. Fishes, 390. 



