This wave-like peculiarity of motion is described in a curious old book, _An Essay towards a Natural History of Serpents_. Charles Owen, D.D. London, 1742: "The Ambua, so the natives of Brazil call the Millepedes and the Centipedes, are serpents. Those reptiles of thousand legs bend as they crawl along, and are reckoned very poisonous. In these Multipedes the mechanism of the body is very curious; in their going it is observable that on each side of their bodies every leg has its motion, one regularly after another, so that their legs, being numerous, form a kind of undulation, and thereby communicate to the body a swifter progression than one could imagine where {41}so many short feet are to take so many short steps, that follow one another rolling on like the waves of the sea." Before proceeding to the classification of Myriapods, which will form the next part of this account, a few words on the common names for them may not be without interest. In English we have the names Centipede and Millepede, and the Continental nations have similar names implying the possession of a hundred or a thousand legs, as the German "Tausendfüsse" and the French "Millepieds." Of course these are general words, simply implying the possession of a great number of legs. But we have also among the peasantry a name for Centipedes which conveys a much more accurate idea of the number. The people of the eastern counties (I daresay the term is more widely spread) call them "forty legs." This is not quite accurate, but as _Lithobius_ has 17 legs on each side, and _Scolopendra_ (_Cryptops_ is the English species) has 21 on each side, it is a better approximation than Centipede. But another country has a still more accurate term. I found some _Scolopendra_ in Beyrout, and asked my native servant what he called them. He gave them what I afterwards found was the common Arab name for them, "‘arba wál ‘arbarin," forty-four legs. Now the Scolopendras, which in hotter climates are the chief representatives of the Centipedes, have actually forty-two legs, or, if the poison claws are counted, forty-four. In looking up the Arab term for Centipede I came across a curious description given of them by Avicenna, the great Arabian physician: "This is an animal known for its habit of going into ears. For the most part it is a palm's length" [about four inches, which is the average length of many species]. "On each side of the body it has twenty-two feet, and moves equally well either backwards or forwards."