"The vegetable kingdom will certainly not be rank and luxurious, because there is not enough sunlight or heat for that; nor will it be gnarled and tough, but more likely spongy and cactus-like. The weak gravity will oppose but a mild resistance to the activity and climbing propensities of vegetable sap, however, which is likely to result in very tall, slender trees. The forces that lie hidden in an acorn should be able to build a most grandly towering oak on Mars. Among the animals the species of upright, two-legged things is apt to abound. There is no reason for four legs when the body weighs but little. On the Earth an extremely strong development of the lower limbs is necessary for upright things, as is shown in the cases of kangaroos and men. In order that a cow might go comfortably on two legs, she would have to be furnished with the hind-legs of an elephant; but not so on Mars. Creeping things would be very few, and it is possible that fish may fly in the water with a short pair of wings. What four-legged animals there are will very likely be large and monstrous; for an enormous animal could exist comfortably and move about easily without clumsiness. For instance, an earthly elephant transferred to Mars would weigh only one-third as much, and so there might well be elephants three times as large as ours, perfectly able to handle themselves with ease." "By the same reasoning then, I suppose the intelligent beings, or what we call men, will be great giants twenty-five feet high?" I put in. "Some have thought so, but I do not at all agree with them," replied the doctor. "I stick to the theory of small men for small planets, and large men for large planets. There is no possible reason for a large man on Mars, where muscular development is uncalled for and useless, and where the inhabitable space is small. If there are men on Jupiter, they must of necessity be enormously strong to hold themselves up and resist gravitation. If they walk upright (which I think unlikely), their legs must be very large and as solid as iron. The Martian legs are likely to be small and puny, and I believe the upper limbs will be much more strongly developed. In fact, on Mars the Creator had His one great opportunity of making a _flying man_, and I do not think He has overlooked it. With a rather small, tightly-knit frame, and the upper limbs developed into wings as long as the body, flying against the weak Martian gravitation would be perfectly easy, and a vast advantage over walking." "Ah! then perhaps they will fly out to meet you!" I ejaculated.