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in ANIMAL LIFE IN THE TROPICAL FORESTS 307liarities.They differ somewhat in dentition and in otherstructural features from all Old World apes, and a considerablenumber of them have prehensile tails, a peculiarity neverfound elsewhere. In the howlers and the spider monkeysthe tail is very long and powerful, and by twisting theextremity round a branch the animal can hang suspended aseasily as other monkeys can by their hands. It is, in fact, afifth hand, and is constantly used to pick up small objectsfrom the ground. The most remarkable of the Americanmonkeys are the howlers, whose tremendous roaring exceedsthat of the lion or the bull, and is to be heard frequently atmorning and evening in the primeval forests. The sound isproduced by means of a large, thin, bony vessel in the throat,into which air is forced ;and it is very remarkable that thisone group of monkeys should possess an organ not found inany other monkey or even in any other mammal, apparentlyfor no other purpose than to be able to make a louder noisethan the rest. The only other monkeys worthy of specialattention are the marmosets, beautiful little creatures withcrests, whiskers, or manes, in outward form resembling squirrels,but with a very small monkey -like face. They are eitherblack, brown, reddish, or nearly white in colour, and are thesmallest of the monkey tribe, some of them being only aboutsix inches long exclusive of the tail.BatsAlmost the only other order of mammals that is speciallyand largely developed in the tropical zone is that of theChiroptera or bats, which becomes suddenly much less plentifulwhen we pass into the temperate regions, and still morerare towards the colder parts of it, although a few speciesappear to reach the Arctic circle. The characteristics of thetropical bats are their great numbers and variety, their largesize, and their peculiar forms or habits. In the East thosewhich most attract the traveller's attention are the great fruitbats,or flying -foxes as they are sometimes called, from therusty colour of the coarse fur and the fox-like shape of thehead. These creatures may sometimes be seen in immenseflocks which take hours to pass by, and they often devastatethe fruit plantationsof the natives. They are often five feet