226 RATE OF GROWTH OF SOME SEA FISHES. 



reversed; one of these sixty-six had a few small patches of pigment 

 on the lower side of the skin, but in no other specimen did any 

 pigment occur on the lower side. 



Thus the largest of these specimens known to be two years of age 

 was 26" 7 cm. long or 10*5 incheSj while the smallest was 7'2 cm. or 

 2"8 inches. I feel convinced myself that this great difference in size is 

 chiefly due to differences in nutrition, produced by the competition for 

 a limited supply of food among a large number of individuals in a 

 confined space. It proves at least that under certain conditions a 

 flounder may be only o inches long when two years old, and it is quite 

 possible that these conditions are sometimesrealised in nature. On the 

 other hand, the size of the larger specimens agrees perfectly with the 

 size of those taken at sea which I had estimated to be of aboutthis age. 



With respect to sexual or reproductive maturity, the spawning 

 season is not yet passed, and some of the specimens now unripe 

 may be found to be ripe in April or even in May. But I am 

 inclined to think that the majority, if not all, of the specimens found 

 to be unripe in February and March will not spawn this year. I 

 was surprised to find the proportion of ripe specimens so small. It 

 was 16 per cent, in the small tank, 20 per cent, in the large, or 

 19 per cent, taking the two together. In my last paper I recorded 

 the fact that none of these captive flounders were ripe at one year 

 of age, and inferred that they would breed for the first time when 

 two years old. It now appears that only a small proportion breed 

 at that age, the majority not attaining to sexual maturity in the 

 second spawning season after that in which they were hatched. It 

 seems probable, therefore, that the greater number of young- 

 flounders breed for the first time when three years old, while a 

 small proportion begin to breed at two years. If this were the case 

 normally in flounders and other flat-fishes, not only under artificial 

 but under natural conditions, then in this respect the life-history of 

 the flat-fish would resemble that of the salmon, which has been so 

 long and so attentively studied. For, according to the account 

 given by Day in his British Fishes, it has been conclusively proved 

 that out of the salmon fry hatched in a given spring, which become 

 parrs in the following summer, a certain small proportion become 

 smolts in the following spring when one year old, and descend to the 

 sea, while the larger number remain in the rivers as parrs until they 

 are two years old, and then migrate as smolts. Now a smolt which 

 descends in spring returns as a grilse the following autumn and 

 spawns. Therefore a proportion of salmon breed for the first time 

 two years after the autumn in which they themselves were spawned, 

 while the majority do not become sexually mature until the third 

 autumn. 



