39 
1879*] wt the Organic World. 
Did a man weigh three times as much as he now does — 
as would be the case were he placed on the surface of 
Jupiter — the conditions of organic life must be still further 
altered, and the resulting forms, other conditions remaining 
equal, would differ still more widely from what we see 
around us. 
Decreased attraction of the earth, or a reduction in the 
aCtual weight of plants and animals, would be attended 
with another set of changes scarcely less remarkable. With 
the same expenditure of vital energy as at present, and with 
the same quantity of transformation of matter, we might be 
able to lift larger bulks, to take longer bounds, to move with 
greater swiftness, and to undergo prolonged muscular exer- 
tion with less fatigue. Hence the transformation of matter 
required to keep up animal heat, and to restore the waste 
of tissue, would be smaller for the same amount of duty 
done. A less volume of blood, smaller lungs and digestive 
organs would be required. The labour of the heart, in 
raising the blood to the head and parts of the body above 
its own level, would be reduced. Hence we might expeCt a 
set of structural changes in terrestrial animals of an inverse 
nature to those we have seen resulting from intensified gra- 
vitation. All parts of the body might safely be constructed 
upon a less massive plan. A slighter skeleton, smaller 
muscles, and a slenderer trunk would suffice. These modi- 
fications would be the more essential from another consider- 
ation. At present the cases in which men or other terrestrial 
animals, are swept away by the wind are exceptional, and 
occur only in furious cyclones. Were our weight, however, 
reduced to one-fourth of its present magnitude, whilst our 
bulk remained unchanged, we should not seldom run the 
risk of being carried off our feet, with the possibility of un- 
pleasant consequences. Hence one of the characteristics 
of the “ fittest ” for survival in such a state of things would 
be either a minimisation of the surface exposed to the wind, 
or the utilisation of atmospheric currents as a means of 
locomotion. On the water this is already done by the paper 
nautilus, which drives before the wind, using its arms as a 
kind of sails. On land we may see that most noxious 
Dipteron the “ Harry long-legs ” ( Tipula oleraceu) travelling 
in a brisk breeze, with a kind of motion that is neither run- 
ning nor flying, but a curious mixture of both. Head-first 
or tail-first, rolling over and over, it makes a very rapid 
progress, as we find if we attempt to “ stamp it out,” though 
all the while its movements appear exceedingly clumsy. 
Were the force of gravitation reduced in the manner we are 
