"The most primitive mammals were probably small insectivorous or omnivorous forms, therefore with simple, short-crowned teeth, of slow-moving, ambulatory, terrestrial, or arboreal habit, and with short feet provided with claws. In seeking food and avoiding enemies in different habitats the limbs and feet radiate in four diverse directions; they either become fossorial or adapted to digging habits, natatorial or adapted to amphibious and finally to aquatic habits, cursorial or adapted to swift-moving, terrestrial progression, arboreal or adapted to tree life. Tree life leads, as its final stage, into
the parachute types of the flying squirrels and phalangers, or into the true flying types of the bats.... Similarly in the case of the teeth, insectivorous and omnivorous types appear to be more central and ancient than either the exclusively carnivorous or herbivorous types. Thus the extremes of carnivorous adaptation, as in the case of the cats, of omnivorous adaptation, as in the case of the bears, of herbivorous adaptation, as in the case of the horses, or myrmecophagous adaptation, as in the case of the anteaters, are all secondary" (loc. cit., pp. 23-4).
We have now reached the end of our historical survey of the problems of form. What the future course of morphology will be no one can say. But one may hazard the opinion that the present century will see a return to a simpler and more humble attitude towards the great and unsolved problems of animal form. Dogmatic materialism and dogmatic theories of evolution have in the past tended to blind us to the complexity and mysteriousness of vital phenomena. We need to look at living things with new eyes and a truer sympathy. We shall then see them as active, living, passionate beings like ourselves, and we shall seek in our morphology to interpret as far as may be their form in terms of their activity.
This is what Aristotle tried to do, and a succession of master-minds after him. We shall do well to get all the help from them we can.
[519] See E. B. Wilson's masterly book, The Cell in Development and Inheritance, New York and London, 1900.
[520] Q.J.M.S., xxvi. 1886.
[521] Wood's Holl Biological Lectures for 1893.
[522] Arch. f. Ent.-Mech., i., pp. 380-90, 1895.
[523] Beiträge zur Kritik der Darwinschen Lehre, Leipzig, 1898.