1. The Canis caraibicus (Lesson), without hair, and which does not bark. 2. The Canis ingae (Tschudi), the common hairy dog, which has pointed nose and ears, and barks.* (* J.J. von Tschudi quoted by Humboldt "Aspects of Nature" English edition volume 1 page 111.) The small eatable dog of the Mexicans was called by them Techichi; and Humboldt derives the name from Tetl, a stone, and says that it means "a dumb dog," but this appears rather a forced derivation. Chichi is Aztec for "to suck;" and it seems to me more probable that the little dogs they eat, and which are spoken of by the Spaniards as making very tender and delicate food, were the puppies of the Xoloitzcuintli, and that Techichi meant "a sucker." Whether the hairless dog was or was not the Techichi of which the Mexicans made such savoury dishes is an open question, but there can be no doubt that the former was found in tropical America by the Spanish conquerors, and that it has survived to the present time, with little or no change. That it should not have intermixed with the common haired variety, and lost its distinctive characters, is very remarkable. It has not been artificially preserved, for instead of being looked on with favour by the Indians, Humboldt states that in Peru, where it is abundant, it is despised and ill-treated. Under such circumstances, the variety can only have been preserved through not interbreeding with the common form, either from a dislike to such unions, or by some amount of sterility when they are formed. This is, I think, in favour of the inference that the variety has been produced by natural and not by artificial selection, for diminished fertility is seldom or never acquired between artificial varieties.