Habit and instinct / by C. Lloyd Morgan.

  • C. Lloyd Morgan
Date:
1896
Catalogue details

Licence: Public Domain Mark

Credit: Habit and instinct / by C. Lloyd Morgan. Source: Wellcome Collection.

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    exist between structure and habit, it must be noted that there are many instinctive activities that no examination of structure, with our present means and appliances, would enable us to foretell. In the tributaries of the Severn there is a spring migration of little eels, or elvers. Thou- sands may be seen swimming up stream, and even surmounting such obstacles as small waterfalls and mill- sluices by wriggling up the conferva-clad surface. But there is nothing in their structure to give a hint of this migratory instinct. If an ant-lion larva were given to a naturalist ignorant of its habits, he would no doubt be able to say that it led a predatory life. He would not infer from its structure that it made a conical pit in the sand to entrap unwary ants and other insects, and, as it lay almost concealed at the apex of the cone, scattered a shower of sand-grains, by which its victim was brought down into its very jaws. No examination of the structure of a limpet would enable us to foretell that it would wander in search of food within a radius of about a yard from its scar, performing its peregrination when the rocks were wetted by the tide, but returning home to its own particular scar on the rock ere the sun and air had baked and dried the surface, and ere the returning tide had deeply sub- merged its home.* Very many such cases might be given of activities to which the study of structure alone would afford no clue. The fact that the same organ often subserves more than one purpose may sometimes lead one astray in attempting to infer habit from structure. In Trinidad there occurs a climbing picarian bird, the red-tailed jacamar (Galbula ruficauda). It has a long, sharp, pointed bill, and no one from a study of its structure would be likely to foretell that it subsists on flies, which it catches * See Nature, vol. xxxi. p. 200; and vol. li. pp. 127 and 511.
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