The mystery of the mongoos and its antidote has been referred to the supposition that there may be some peculiarity in its organisation which renders it _proof against_ the poison of the serpent. It remains for future investigation to determine how far this conjecture is founded in truth; and whether in the blood of the mongoos there exists any element or quality which acts as a prophylactic. Such exceptional provisions are not without precedent in the animal oeconomy: the hornbill feeds with impunity on the deadly fruit of the strychnos; the milky juice of some species of euphorbia, which is harmless to oxen, is invariably fatal to the zebra; and the tsetse fly, the pest of South Africa, whose bite is mortal to the ox, the dog, and the horse, is harmless to man and the untamed creatures of the forest.[1] [Footnote 1: Dr. LIVINGSTONE, _Tour in S. Africa_, p. 80. Is it a fact that, in America, pigs extirpate the rattlesnakes with impunity?] The Singhalese distinguish one species of mongoos, which they designate "_Hotambeya_" and which they assert never preys upon serpents. A writer in the _Ceylon Miscellany_ mentions, that they are often to be seen "crossing rivers and frequently mud-brooks near Chilaw; the adjacent thickets affording them shelter, and their food consisting of aquatic reptiles, crabs, and mollusca."[1] [Footnote 1: This is possibly the "musbilai" or mouse-cat of Behar, which preys upon birds and fish. Can it be the Urva of the Nepalese (_Urva cancrivora_, Hodgson), which Mr. Hodgson describes as dwelling in burrows, and being carnivorous and ranivorous?--Vide _Journ. As. Soc. Beng._ vol. vi. p. 56.] [Illustration: FLYING SQUIRREL.] IV. RODENTIA. _Squirrels_.--Smaller animals in great numbers enliven the forests and lowland plains with their graceful movements. Squirrels[1], of which there are a great variety, make their shrill metallic call heard at early morning in the woods; and when sounding their note of warning on the approach of a civet or a tree-snake, the ears tingle with the loud trill of defiance, which rings as clear and rapid as the running down of an alarum, and is instantly caught up and re-echoed from every side by their terrified playmates. [Footnote 1: Of two kinds which frequent the mountains, one which is peculiar to Ceylon was discovered by Mr. Edgar L. Layard, who has done me the honour to call it the _Sciurus Tennentii_. Its dimensions are large, measuring upwards of two feet from head to tail. It is distinguished from the _S. macrurus_ by the predominant black colour of the upper surface of the body, with the exception of a rusty spot at the base of the ears.]