128 EXTINCT MONSTERS 
fishes ; the original land mammal from which whales are descended 
has, in the course of time, become so fish-like in appearance 
that even in these modern days there are some who yet speak 
of them as fishes! The shape of a whale is fish-like; it has 
lost its hind limbs through disuse; it has changed its fore 
limbs into paddles, which have a certain fin-like aspect; and 
its cousin, the porpoise, has developed a big triangular fin on the 
back. To take another example: Pterodactyls are reptiles which 
acquired the power of flight; and some, at least, of them must 
have borne a resemblance to modern bats. And yet pterodactyls 
and bats are in no way related. The pterodactyl was a lizard 
that could fly; while the bat is a mammal that can do the 
same. There is no question of relationship. Now let us apply 
the same kind of reasoning to Dinosaurs and birds. For our 
part, we confess to being not quite convinced. Dinosaurs walked, 
ran, and perhaps some of the smaller ones even hopped on their 
hind legs; would it not follow as a matter of course that certain 
rather bird-like developments would follow? Let us reason the 
matter out. For a horizontal body, lke that of a lizard, to be 
properly poised on two legs instead of four, the weight of the 
viscera must be transferred backward, and the forward, or anterior 
part of the body lightened. The lower bones of the region of 
the hips (pelvis), with the contained organs, are thrown back- 
ward, while the fore part of the body and the fore limbs are 
lightened and much reduced in proportionate size. 
Changes such as these might be supposed capable of producing 
those bird-like features in Dinosaurs which we have already 
noticed, and on the strength of which some authorities believe 
birds and Dinosaurs to have had a common ancestry. It may 
perhaps be safer to look upon the ancestry of birds as one of 
those problems that remain to be solved by some future 
