THE FLAT-FISHES 219 



emerges from the egg, to the distorted shape of the adult, 

 occupies about six weeks. The yolk-sac disappears in eight 

 days, and the larva is now entirely dependent on other food, 

 to which, however, it probably accustoms itself gradually 

 even before nature's supply is exhausted. This early food 

 consists of diatoms ; at a later stage the little fish would 

 be able to devour copepoda ; and finally it would chase small 

 shrimps. By the beginning of the seventh week the little 

 plaice swims in its new position, the left eye lies alongside 

 the right, the head is twisted out of its former plane, and 

 the left side loses all colour. Larval flat-fishes are preyed 

 on in these early days by jelly-fishes, and Masterman figures 

 one {op. cit., p. 56) swallowing a tiny flounder. 



The rate of growth of the plaice has been much discussed. 

 Observations are necessarily based on either examples reared 

 under artificial conditions, or else on the spoils of the tow- 

 net, with gaps and uncertainties that render positive pro- 

 nouncements extremely difficult. As a case of actual 

 experiment, Dannevig found that plaice on the Scotch coast 

 grew about 3 in. in the year, most of this increment being 

 credited to the warmer months. This yearly growth is, 

 however, known only up to the third year inclusive. 



The size at which the plaice becomes mature — that is to 

 say, capable of depositing or fertilising ova, is of great 

 importance (see Chapter II.) in all questions of prohibitive 

 legislation. It would seem that the male is always mature 

 at a smaller size than the female ; but these sizes vary 

 according to locality, and it is this variation that furnishes 

 the chief obstacle to legislation. Thus, Cunningham gives 

 15 in. for the Channel; Holt 17 in. for the North Sea; 

 and Petersen much lower sizes (10-13 in.) for the Danish 

 coast. 



The plaice is generally distributed round the British 

 Islands, but the larger fish keep out in the deeper water, up 

 to about 100 fathoms, outside of which line none are caught. 



