Those who have watched a larval cod about 4 mm. in length nimbly avoiding the forceps following it for capture are in a fair way to estimate the brain-functions of an adult measuring three feet. Still more is this appreciation of such functions strengthened by the behaviour of a large grey skate in its endeavour to escape over a trawl-beam more than fifty feet long which had been arrested in its rise—just above the surface of the sea—by a temporary block in the machinery. The dexterity with which it skimmed to and fro along the beam to find where it dipped sufficiently during the movements of the ship to enable it to glide over was a study, and relief was felt when at last its intelligent perseverance was rewarded. The observation of a group of salmon on a spawning-bed, and the acquired skill of young trout in passing up a model of a salmon-ladder, are corroborative of both intelligence and memory. Moreover, if those who have given a green cod of six or eight inches a particular kind of “scale-back” (a kind of worm), and noticed, firstly, how eagerly it seized it, then tested it in its pharyngeal region, and soon ejected it, never again taking that species into its mouth, would be slow to deny that fishes, and even very young fishes, have a memory. It is well known that fishes prefer certain kinds of bait to others, probably because they retain the pleasant sensations of former occasions. Thus it is that anemones are a fatal bait for cod, lob-worms and certain Nereids for plaice, the toothsome mussel for most marine fishes, and the stripe of silvery skin (like a young rockling or mackerel-midge) so eagerly sought by the mackerel. Muddy water, again, obscures the nature of bait, and misleads both observation and memory, so that a lure which would not so readily capture in clear water is now effective, because no suspicions are roused. On the other hand, the presence of phosphorescent organisms on a mackerel- or herring-net is said to prevent a successful haul.
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