Part 25 (1/2)

THE AUSTRALIAN MORE-PORK OR PODARGUS

A bird with a frog-like mouth, allied to the British Nightjar. Now in the London Zoological Gardens.

The capacious mouth is well suited for engulfing large insects such as locusts and mantises, which are mostly caught on the trees. During the day the More-pork or Frog-mouth sleeps upright on a branch, and its mottled brown plumage makes it almost invisible.]

[Ill.u.s.tration: PELICAN'S BILL, ADAPTED FOR CATCHING AND STORING FISHES

There is an enormous dilatable sac beneath the lower jaw.]

[Ill.u.s.tration: HORNBILL'S BILL, ADAPTED FOR EXCAVATING A NEST IN A TREE, AND ALSO FOR SEIZING AND BREAKING DIVERSE FORMS OF FOOD, FROM MAMMALS TO TORTOISES, FROM ROOTS TO FRUITS

The use of the helmet or casque is obscure.]

[Ill.u.s.tration: SPOONBILL'S BILL, ADAPTED FOR SIFTING THE MUD AND CATCHING THE SMALL ANIMALS, E.G. FISHES, CRUSTACEANS, INSECT LARVae, WHICH LIVE THERE]

[Ill.u.s.tration: FALCON'S BILL, ADAPTED FOR SEIZING, KILLING, AND TEARING SMALL MAMMALS AND BIRDS]

[Ill.u.s.tration: AVOCET'S BILL, ADAPTED FOR A CURIOUS SIDEWAYS SCOOPING IN THE Sh.o.r.e-POOLS AND CATCHING SMALL ANIMALS]

[Ill.u.s.tration: PUFFIN'S BILL, ADAPTED FOR CATCHING SMALL FISHES NEAR THE SURFACE OF THE SEA, AND FOR HOLDING THEM WHEN CAUGHT AND CARRYING THEM TO THE NEST

The scaly covering is moulted in the autumn.]

We must not dwell too long on this particular instance of evolution, though it has meant much to our race. We wish, however, following Professor Buller's _Essays on Wheat_ (1919), to explain the method by which this good seed was discovered. From one we may learn all. The parent of Marquis Wheat on the male side was the mid-Europe Red Fife--a first-cla.s.s cereal. The parent on the female side was less promising, a rather nondescript, not pure-bred wheat, called Red Calcutta, which was imported from India into Canada about thirty years ago. The father was part of a cargo that came from the Baltic to Glasgow, and was happily included in a sample sent on to David Fife in Ontario about 1842. From one kernel of this sample David Fife started his stock of Red Fife, which was crossed by Dr. Saunders with Hard Red Calcutta. The result of the cross was a medley of types, nearly a hundred varieties altogether, and it was in scrutinising these that Dr. Saunders. .h.i.t upon Marquis. He worked steadily through the material, studying head after head of what resulted from sowing, and selecting out those that gave most promise.

Each of the heads selected was propagated; most of the results were rejected; the elect were sifted again and yet again, and finally Marquis Wheat emerged, rich in constructive possibilities, probably the most valuable food-plant in the world. It is like a romance to read that ”the first crop of the wheat that was destined within a dozen years to overtax the mightiest elevators in the land was stored away in the winter of 1904-5 in a paper packet no larger than an envelope.”

Thus from the Wild Wheat of Mount Hermon there evolved one of the most important food-plants of the world. This surely is _Evolution going on_.

-- 2

Changes in the Animal Life of a Country

Nothing gives us a more convincing impression of evolution in being than a succession of pictures of the animal life of a country in different ages. Dr. James Ritchie, a naturalist of distinction, has written a masterly book, _The Influence of Man on Animal Life in Scotland_ (1920), in which we get this succession of pictures. ”Within itself,” he says, ”a fauna is in a constant state of uneasy restlessness, an a.s.semblage of creatures which in its parts ebbs and flows as one local influence or another plays upon it.” There are temporary and local changes, endless disturbances and readjustments of the ”balance of nature.” One year there is a plague of field-voles, perhaps next year ”grouse disease” is rife; in one place there is huge increase of starlings, in another place of rabbits; here c.o.c.kchafers are in the ascendant, and there the moles are spoiling the pasture. ”But while the parts fluctuate, the fauna as a whole follows a path of its own. As well as internal tides which swing to and fro about an average level, there is a drift which carries the fauna bodily along an 'irretraceable course.'” This is partly due to considerable changes of climate, for climate calls the tune to which living creatures dance, but it is also due to new departures among the animals themselves. We need not go back to the extinct animals and lost faunas of past ages--for Britain has plenty of relics of these--which ”ill.u.s.trate the reality of the faunal drift,” but it may be very useful, in ill.u.s.tration of evolution in being, to notice what has happened in Scotland since the end of the Great Ice Age.

Some nine thousand years ago or more, certain long-headed, square-jawed, short-limbed, but agile hunters and fishermen, whom we call Neolithic Man, established themselves in Scotland. What was the state of the country then?

It was a country of swamps, low forests of birch, alder, and willow, fertile meadows, and snow-capped mountains. Its estuaries penetrated further inland than they now do, and the sea stood at the level of the Fifty-Foot Beach. On its plains and in its forests roamed many creatures which are strange to the fauna of to-day--the Elk and the Reindeer, Wild Cattle, the Wild Boar and perhaps Wild Horses, a fauna of large animals which paid toll to the European Lynx, the Brown Bear and the Wolf. In all likelihood, the marshes resounded to the boom of the Bittern and the plains to the breeding calls of the Crane and the Great Bustard.

Such is Dr. Ritchie's initial picture.

[Ill.u.s.tration: LIFE-HISTORY OF A FROG

1, Before hatching; 2, newly hatched larvae hanging on to water-weed; 3, with external gills; 4, external gills are covered over and are absorbed; 5, limbless larva about a month old with internal gills; 6, tadpole with hind-legs, about two months old; 7, with the fore-limbs emerging; 8, with all four legs free; 9, a young frog, about three months old, showing the almost complete absorption of the tail and the change of the tadpole mouth into a frog mouth.]

[Ill.u.s.tration: _Photo: J. J. Ward. F.E.S._

HIND-LEG OF WHIRLIGIG BEETLE WHICH HAS BECOME BEAUTIFULLY MODIFIED FOR AQUATIC LOCOMOTION

The flattened tips form an expanding ”fan” or paddle, which opens and closes with astonis.h.i.+ng rapidity. The closing of the ”fan,” like the ”feathering” of an oar, reduces friction when the leg is being moved forwards for the next stroke.]