Page:The Zoologist, 4th series, vol 1 (1897).djvu/428

400 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 flatfish, 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