i879-1 
in the Organic World . 
37 
or the distance through which the blood would require to 
be impelled must be reduced, and the vessels widened so that 
there might be less loss from fridtion. The increased amount 
of nutriment required would involve a corresponding increase 
in the difficulty of its collection, and the struggle for existence 
would therefore probably be intensified. 
These considerations involve a very marked change 
in the structure of land animals. Their general form, 
in accordance with their thickened bones, increased muscles, 
and larger respiratory and digestive apparatus, would be 
heavier and more massive than what we now observe. 
The necessity for such a structure would be increased 
by another circumstance, viz., that the probability of a 
fall, and the danger, if it should happen, would both be 
increased. Hence the bipedal form — whether among an- 
thropoids, birds> or hopping lizards — would be attended with 
much greater drawbacks than is the case with the actual 
amount of gravitative force. Even quadrupeds would be un- 
safe in their movements, and it is highly probable that a 
hexapod, octopod, or decapod structure would be found ex- 
tending much higher in the animal kingdom than it does in 
our world. Or if there is some reason why the number of 
limbs in a vertebrate animal cannot exceed four, we should 
find the majority of animals furnished with short legs, like 
those of Saurians, which raise the trunk of the body but 
little, and allow it to rest easily upon the surface of the 
ground. The type which we see in serpents would probably 
be much more common, and would be developed into a great 
variety of forms. The necessity of keeping the centre of 
gravity low, and the great demands made upon the system 
in other respecfts, would conspire to reduce the size of the 
head and the brain. 
Of all animals those which pass a large proportion of 
their existence in the air, supported upon wings, would meet 
with the greatest difficulties. The earth would draw them 
down with a force hard to resist, and which could only be 
overcome by the expenditure of a large amount of muscular 
force, and consequently of the transformation of much 
matter. Hence with gravitation intensified, as we are sup- 
posing, such forms of life as the humming-birds, the swifts, 
the swallows, &c., could scarcely exist. In their stead 
would flourish groups approaching to the Gallinacese and 
the Struthionidse, along with the true woodland birds, whose 
flight is little more than an extended leap from branch to 
branch. 
Winged inserts would fare very similarly to birds. The 
