It is not easy to be sure exactly how the backboned animals began, but the best clue we have to the mystery is found in a little half-transparent creature about two inches long, which is still to be found living upon our coast. This small insignificant animal is called the “Lancelet,”[4] because it is shaped something like the head of a lance, and it is in many ways so imperfect that naturalists believe it to be a degraded form, like the acorn-barnacle; that is to say, that it has probably lost some of the parts which its ancestors once possessed. But in any case it is the most simple backboned animal we have, and shows us how the first feeble forms may have lived. [Illustration: Fig. 1. The Lancelet, _the lowest known fish-like form_. _m_, mouth. _e_, eye-spot. _f_, fin. _r_, rod or notochord, the first faint indication of a backbone. _nv_, nerve cord. _g_, gills. _h_, hole out of which water passes from the gills. _v_, vent for refuse of food. ] Flitting about in the water near the shore, eating the minute creatures which come in his way, this small fish-like animal is so colourless, and works his way down in the sand so fast at the slightest alarm, that few people ever see him, and when they do are far more likely to take him, as the naturalist Pallas did, for an imperfect snail than a vertebrate animal. He has no head, and it is only by his open mouth (_m_), surrounded by lashes with which he drives in the microscopic animals, that you can tell where his head ought to be. Two little spots (_e_) above his mouth are his feeble eyes, and one little pit (_n_) with a nerve running to it is all he has to smell with. He has no pairs of fins such as we find in most fishes, but only a delicate flap (_f_) on his back and round his tail; neither has he any true breathing-gills, but he gulps in water at his mouth, and passes it through slits in his throat into a kind of chamber, and from there out at a hole (_h_) below. Lastly, he has no true heart, and it is only by the throbbing of the veins themselves that his colourless blood is sent along the bars between the slits, so that it takes up air out of the water as it passes.