e present day, we may say that they made among other acquisitions the
following: true ventral lungs, a three-chambered heart, a movable
tongue, a drum to the ear, and lids to the eyes. It is very interesting
to find that though the tongue of the tadpole has some muscle-fibres in
it, they are not strong enough to effect movement, recalling the tongue
of fishes, which has not any muscles at all. Gradually, as the tadpole
becomes a frog, the muscle-fibres grow in strength, and make it possible
for the full-grown creature to shoot out its tongue upon insects. This
is probably a recapitulation of what was accomplished in the course of
millennia in the history of the Amphibian race. (4) Another acquisition
made by Amphibians was a voice, due, as in ourselves, to the rapid
passage of air over taut membranes (vocal cords) stretched in the
larynx. It is an interesting fact that for millions of years there was
upon the earth no sound of life at all, only the noise of wind and wave,
thunder and avalanche. Apart from the instrumental music of some
insects, perhaps beginning in the Carboniferous, the first vital sounds
were due to Amphibians, and theirs certainly was the first voice--surely
one of the great steps in organic evolution.

[Illustration: _Photo: British Museum (Natural History)._

FOSSIL OF A PTERODACTYL OR EXTINCT FLYING DRAGON

The wing is made of a web of skin extended on the enormously elongated
outermost finger. The long tail served for balancing and steering. The
Pterodactyls varied from the size of sparrows to a wing-span of fifteen
feet--the largest flying creatures.]

[Illustration: _From Knipe's "Nebula to Man."_

PARIASAURUS: AN EXTINCT VEGETARIAN TRIASSIC REPTILE

Total length about 9 feet. (Remains found in Cape Colony, South
Africa.)]

[Illustration: _From Knipe's "Nebula to Man."_

TRICERATOPS: A HUGE EXTINCT REPTILE

(From remains found in Cretaceous strata of Wyoming, U.S.A.)

This Dinosaur, about the size of a large rhinoceros, had a huge
three-horned skull with a remarkable bony collar over the neck. But, as
in many other cases, its brain was so small that it could have passed
down the spinal canal in which the spinal cord lies. Perhaps this partly
accounts for the extinction of giant reptiles.]

[Illustration: _Photo: "Daily Mail."_

THE DUCKMOLE OR DUCK-BILLED PLATYPUS OF AUSTRALIA

The Duckmole or Duck-billed Platypus of Australia is a survivor of the
most primitive mammals. It harks