The general characteristic of the Tree-snake is an exceedingly thin and delicate body, often adorned with colours exquisite as those of the foliage amongst which they live concealed. In some of the South American species the tints vie in brilliancy with those of the humming-birds; whilst their forms are so flexible and slender as to justify the name conferred on them of "_whip-snakes_." The Siamese, to denote these combinations of grace and splendour, call them "Sun-beams." A naturalist[1], describing a bright green species in Brazil (_Philodryas viridissimus_), writes: "I am always delighted when I find that another tree-snake has settled in my garden. You look for a bird's nest, the young ones have gone, but you find their bed occupied by one of these beautiful creatures, which will coil up its body of two feet in length within a space no larger than the hollow of your hand. They appear to be always watchful; for at the instant you discover one, the quick playing of the long, black, forked tongue will show you that you too are observed. On perceiving the slightest sign of your intention to disturb it, the snake will dart upwards through the branches and over the leaves which scarcely appear to bend beneath the weight. A moment more, and you have lost sight of it. Whenever I return to Europe, you may be sure that in my hot-house those harmless, lovely creatures shall not be missing." [Footnote 1: Dr. WUCHERER of Bahia.] [Illustration: TREE SNAKE. Passerita fusca.] Ceylon has several species of Tree-snakes, and one of the most common is the green _Passerita_, easily recognized from its bright colour and from the pointed moveable appendage, into which the snout is prolonged. The snakes of this genus being active chiefly during the night, the pupil of the eye is linear and horizontal. They never willingly descend from trees, but prey there upon nocturnal Saurians, geckoes, small birds and their young; and they are perfectly harmless, although they often try to bite. It is strange that none of the numerous specimens which it has been attempted to bring to Europe have ever fed in captivity; whilst in South America they take their food freely in confinement, provided that some green plants are placed in their cage. In Ceylon I have never seen any specimen of a larger size than three feet; whilst they are known to attain to more than five on the Indian Continent.