586 THE LANCELET. 



with a single hooked tooth upou the palate, serving apparently as an 

 organ of prehension, and the tongue is supplied with a double row of 

 smaller but powerful teeth on each side, acting on the principle of a 

 rasp. The Myxine can scarcely be said to possess any bones, the only 

 indication of a skeleton being the vertebral column, which is nothing 

 more than a cartilaginous tube, through which a probe can be passed in 

 either direction. 



The color of the Hag-fish is dark brown above, taking a paler tint 

 on the sides, and grayish yellow below. Its length is generally about 

 a foot or fifteen inches. 



The last of the fishes is a creature so unfishlike that its real position 

 in the scale of nature was long undecided, and the strange little being 

 has been bandied about between the vertebrate and invertebrate classes. 

 Between these two great armies the Lancelet evidently occupies the 

 neutral ground, its structure partaking with such apparent equality of 

 the characteristics of each class that it could not be finally referred to 

 its proper rank until it had been submitted to the most careful dissec- 

 tions. In fact, it holds just such a position between the vertebrates and 

 the invertebrates as does the lepidosiren between the reptiles and the 

 fishes. 



It has no definite brain — at all events, it is scarcely better defined 

 than in many of the insect tribe, and only marked by a rather increased 

 and blunted end of the spinal cord. It has no true heart, the place of 

 that organ being taken by pulsating vessels, and the blood being quite 

 pale. It has no bones, the muscles being merely attached to soft carti- 

 lage, and even the spinal cord is not protected by a bony, or even horny, 

 covering. The body is very transparent, and is covered by a soft deli- 

 cate skin without any scales. There are no eyes and no apparent ears, 

 and the mouth is a mere longitudinal fissure under that part of the body 

 which we are compelled, for want of a better term, to call the head, 

 and its orifice is crossed by numerous cirrhi, averaging from twelve 

 to fifteen on each side. Altogether, it really seems to be a less per- 

 fect and less developed animal than many of the higher molluscs. 



The general aspect of the Lancelet is not unlike that of another fish 

 called the leptocephalus, the delicate transparent body and the diagonal 

 arrangement of the muscles causing a considerable resemblance between 

 the two. But the leptocephalus is at once distinguished by its head, 

 which, although very small in proportion to the body, is yet perfect, 

 possessing well-developed eyes, gill-covers, jaws, and teeth ; whereas 

 the Lancelet has no particular head, and neither eyes, gill-covers, 

 jaws, nor teeth. 



