I may here call attention to one fact concerning the arboreal habit. There appears to be a rule to which this habit conforms. Among apes and monkeys the habit is in keeping with the size of the animal. The largest monkeys are found only among the lowest trees, and the small monkeys among the taller trees. It is a rare thing to see a large monkey in the top of a tall tree. He may venture there for food or to make his escape, but it is not his proper element. The same rule appears to hold good among the apes. The gibbon has the arboreal habit in a more pronounced degree than any other true ape. The orang appears to be next; the chimpanzee comes in for third place, and the gorilla last. It must not be understood that all of these apes do not frequently climb, even to the tops of the highest trees; but that is not their normal mode of life, any more than the top of a mast is the habitual place for a sailor on a ship. The chimpanzee is nomadic in habit, and, like the gorilla, seldom or never passes two nights in the same spot. As to his building huts or nests in trees or elsewhere, I am not prepared to believe that he ever does that. For months I hunted in vain and made diligent inquiry in several tribes, but failed to find a specimen of any kind of shelter built by an ape. I do not assert that it is absolutely untrue that he does this, but I have never been able to obtain any evidence of it, except the statement of the natives. On the contrary, certain facts point to the opposite belief. If the ape built himself a permanent home, the natives would soon discover it and there would be no difficulty in having it pointed out. If he built a new one every night, however rude and primitive it might be, there would be so many of them in the forest that there would be no difficulty in finding them. The nomadic habit plainly shows that he does not build the former kind, and the utter absence of them shows that he does not build the latter kind. The whole story appears to be without foundation. In addition to these facts, one thing to be noticed is that few or none of the mammals of the tropics ever build any kind of home. The animals that in other climates have the habit of burrowing do not appear to do so in the tropics, This is due, no doubt, to the warm climate, in which they are not in need of shelter. Of course birds and other oviparous animals build nests, as they do elsewhere. The period of incubation makes this necessary.