Page:The Zoologist, 4th series, vol 1 (1897).djvu/425

Rh they take to swarming in the inshore and estuaries—in this respect the opposite of the ways of the Cod.

With regard to the Clupeidæ (Herring family), Mcintosh and Masterman say that:—"In the case of the four common Clupeoid species—the Herring, Sprat, Pilchard, and Anchovy—the most superficial examination of their eggs with the naked eye is sufficient to distinguish them. The opacity and thick adhesive membrane of the first, the translucence and delicate capsule of the second, the clear peri-vitelline space and oil-globule of the third, and the unique shape (ovoid) of the last are all characters readily recognizable without the assistance of the lens."

Size alone distinguishes the Gadoid eggs. The Herring's egg belongs to the sunken type (demersal), a feature not shared by its immediate family allies, nor of the Cod and flat-fish families; these groups embracing the chief economic British fishes. It is this very exceptional circumstance, together with the occasional eccentric periodic migratory habit of the fish itself, that has compelled the Government repeatedly to recognize the necessity for inquiry into the creature's ways, as a matter involving the nation's fisheries' welfare.

The fluctuations in the Herring fishery can scarcely yet be satisfactorily accounted for, though the hue and cry against trawling is met by the reply that the spawning areas, so far as is known, are not those usually frequented by the trawlers.

There is a slight excess of males among Herring. The female carries from 20,000 to 50,000 ova. Spawning time varies round the coast. Experiments instituted by Dr. Meyer, of Kiel, and corroborated by other observers, prove that temperature of the water materially influences the hatching process. Though seven to ten days is the normal period, cold may vary this to forty days, and pari passu the size of larvæ. When first hatched the larva is more advanced than in the Sprat, a buoyant egg-form. The larval Herring has a biggish head, attenuated colourless body, and the gut passes to proximal tail-end; a broad fin-membrane extends posteriorly from yolk-sac uniformly over back and belly. In the early post-larval stages growth is lengthwise, thickening of body not increasing in the same ratio. There is yet absence of scales or silvery sheen. Later on, however, fins differentiate, the anus acquires a more forward position, the body deepens,