Page:The Zoologist, 4th series, vol 1 (1897).djvu/424

396 spheres, at first scarcely visible, float freely, and in still water rise to the surface. The embryo hatches about the eighth or tenth day. At first the larval Cod are impelled about helplessly, often the yolk-sac uppermost. These tiny fish have black transverse bars, giving them quite a characteristic appearance. In a week's time the yolk-sac is absorbed—the post-larval stage—and the barred pigmentation becomes tesselated or tartan-like. The future back and belly fins are originally continuous membranes. When about three weeks old the head becomes pigmented, while the body assumes more of a greenish yellow hue. Shortly after there is budding of ventral and separation of dorsal fins, and a tendency to longitudinal pigmentation of the body. When arrived at about an inch long or over, the fish has assumed quite an adult facies, with barbel and fins complete. From the rock-pools and upper water they descend among the shore algæ. By the late autumn they are four or five inches, and by the spring a foot long. A seaward migration then takes place, and in their third or fourth year they return in immense companies as full-grown Cod.

Sexual maturity, according to Holt, is when the Cod are from twenty-two inches to three feet long, though Mcintosh is inclined to deem twenty inches a fair average. Quite a variety of annelids, crustaceans, and fish form the Cod's diet; but it is a most voracious, indiscriminate feeder.

The embryology, post-larval up to the adult stages, of other members of the Cod family have in similar manner received assiduous attention. Besides the movements, the food and the everyday life of the fish themselves in their marine habitat have been carefully watched on all parts of the British coasts, both within (shorewise) and beyond the territorial limits. Thus a mass of evidence and information has accrued, practically instructive alike to fishermen and scientific seekers.

The young Ling undergoes remarkable transformation in colour and in curtailment of ventral fins, which in the early stage are relatively of enormous length. The eggs of the Torsk and Ling are distinguished by a great oil-globule, which renders them more conspicuous in the water than those of their allies. The Haddock, and to some extent the Whiting, keep to deep water offshore grounds till reaching five or six inches in length, when