294 



CHARACTERS OF VERTEBRATE ANIMALS 



fishermen use it as bait. The translucent body varies in length 

 from about ij^ inch to rather more than double that size, 

 and at first glance one might be puzzled to say which was the 

 front end of the body, as no distinct head is present. On closer 

 inspection, however, a little hood-like structure, fringed by slender 



EYE NOTOCHORD KIDNEY jTUBULES SPINAL CORO MUSCLES 



LIVER ATRIOPORE 



DORSAL FIN 



.SPINAL NERVE 



B SPINAL NERVE 



MU6CLE6 



KIDNEY TUBULE' 



EPIDERMIS 

 'SPINAL CORD 



NOTOCHORD 



DORSAL ARTERY 



DORSAL GROOVE 

 CCEL'OM 



-ATR^AL CAVITV 



Fig. 170. — Lancelet [Atuphioxus ZanceoJatus) 



A, Side View, with internal organs seen by transparency. Semidiagrammatic. b, Transverse section. 

 Much enlarged and semidiagrammatic. 



tentacles, can be seen near one extremity. This marks the under 

 side of the head end, and, since it leads to the mouth, has been 

 called the oral hood, which has a certain resemblance to the 

 mouth sucker of a Lamprey. Here as there jaws are absent, 

 and the Lancelet is further devoid of the tooth-like projections 

 and powerful rasping tongue which distinguish the Lamprey. 

 Running along the upper margin of the body is a narrow dorsal 

 Jin, passing behind into a slightly expanded caudal fin, which again 



