400 THE ZOOLOGIST. 



but after the introduction of trawling into the North Sea, of 

 steam, and especially railways, with the use of ice, they regularly 

 found their way to interior markets in quantity in the fresh 

 condition. Herring and Cod of yore were the grand staple of 

 fish-trade in this country and the Continent ; yea, much rivalry 

 and many a pretty local and international quarrel arose thereon. 

 Even yet witness the Newfoundland grievance. 



There are quite a number of species of Pleuronectid food-fish 

 in household use. If not individually of the most intrinsic value, 

 yet collectively the Plaice probably heads the list in mercantile 

 superiority. Its life-history consequently has received due 

 attention. Broadly speaking, the old fish are quite offshore 

 dwellers, whereas the young are estuarine, bay and sandy shore 

 frequenters. The cycle pursued is thus traced. The ovarium 

 may contain from 250,000 to double that number, the spawning 

 process being by driblets. It is the earliest spawner of the flat- 

 fish, commencing in January or prior to that date. The egg, of 

 large dimensions, is pelagic, with striated capsule and minus oil- 

 globule. Incubation varies according to temperature, &c. At 

 St. Andrews, in April, eight or nine days ; at Dunbar, in January, 

 sixteen to eighteen days; at Granton, in (?), twenty-seven days. 

 The newly -hatched Plaice resemble the Flounder and Dab, but are 

 larger, viz. about one-fifth of an inch. The mouth is closed, the 

 gut opens immediately behind the yolk, pigmentation is diffuse, the 

 eyes are on each side of a deep, vertically compressed body, and 

 there are broad marginal fin-membranes. From larval to post- 

 larval stage there is a gradual descent from surface to mid-water, 

 and then to bottom. Then turning upon their left side, this 

 loses its pigment by absence of light, whilst the left eye begins to 

 pass towards the right one. Meantime the young fishes by degrees 

 travel shorewards. When verging on half an inch long the body 

 broadens, the eye has got well towards the right, the dorsal fin 

 has advanced to its hinder border, the lateral line looms up, and 

 brown pigment is diffused throughout the upper or right surface 

 of the fish. Growth meanwhile proceeds apace. When a couple 

 of months are over it may be about one inch long, at eight months 

 three inches, a year old four and a half inches, when sixteen to 

 eighteen months reaching about six inches long. Towards the 

 end of second year it averages ten inches, and in the spring of 



