massive cuirass
and weapons of defense are well matched with its teeth and claws. The
momentum of its huge body involved a seemingly slow and lumbering
action, an inertia of its movements, difficult to start and difficult
to shift or to stop. Such movements are widely different from the
agile swiftness which we naturally associate with a beast of prey. But
an animal which exceeds an average elephant in bulk, no matter what
its habits, is compelled by the laws of mechanics to the ponderous
movements appropriate to its gigantic size. These movements, directed
and controlled by a reptilian brain, must needs be largely automatic
and instinctive. We cannot doubt indeed that the Carnivorous Dinosaurs
developed, along with their elaborately perfected mechanism for
attack, an equally elaborate series of instincts guiding their action
to effective purpose; and a complex series of automatic responses to
the stimulus afforded by the sight and action of their prey might
very well mimic intelligent pursuit and attack, always with certain
limits set by the inflexible character of such automatic adjustments.
But no animal as large as _Tyrannosaurus_ could leap or spring upon
another, and its slow stride quickening into a swift resistless rush,
might well end in unavoidable impalement upon the great horns of
_Triceratops_, futile weapons against a small and active enemy, but
designed no doubt to meet just such attacks as these. A true picture
of these combats of titans of the ancient world we cannot draw;
perhaps we will never be able to reconstruct it. But the above
considerations may serve to show how widely it would differ from the
pictures based upon any modern analogies.

One may well inquire why it is that no such gigantic carnivora have
evolved among the mammalian land animals. The largest predaceous
quadrupeds living today are the lion and tiger. The bears although
some of them are much larger, are not generally carnivorous, except
for the polar bear, which is partly aquatic, preying chiefly upon
seals and fish. There are indeed carnivorous whales of gigantic size,
but no very large land carnivore. There were, it is true, during the
Tertiary and Pleistocene, lions and other carnivores considerably
larger than the living species. But none of them attained the size of
their largest herbivorous contemporaries, or even approached it. Among
the dinosaurs on the other hand we find that--setting aside
Brontosaurus and its allies as a