Putnam.] 



128 [Nov. 5, 



ing life, there is exuded a mass of mucus that renders these, of all 

 animals, the most slimy. There are no eyes. 1 The brain is small, 

 but of the normal fish type, and without special development of its 

 parts. There are no pectoral or ventral fins, or any internal struc- 

 ture corresponding to the bones of the pectoral arch, or to the pelvis. 

 The median fins are developed, and the united dorsal, caudal, and 

 anal fins are supported by fine cartilaginous rays. The skull is but 

 slightly developed as a cartilaginous box, and the flexible notochord 

 enclosed in its sheath, and extending from the base of the skull to 

 the end of the tail, is all there is to represent a spinal column. 

 There are no jaws, and the mouth is round and suctorial, without 

 lips, and provided with a pair of barbels on the right and left sides. 

 At the very extremity of the head, on the median line above, is a 

 single nasal aperture, which is provided with two pair of barbels, 

 and opens into the upper part of the mouth. This large nasal cavity 

 is furnished with nerve fibres from the broad fringes of the olfactory 

 nerves, which penetrate it from behind, and it is evidently a very im- 

 portant organ ; smell being the most developed sense of this low ani- 

 mal. The teeth consist of a single median one on the roof of the 

 mouth, and two rows on each side of the tongue, which is a powerful 

 organ, with a strong fibrous tendon moving in a muscular sheath. 

 With the exception of a slight contraction at a point opposite the 

 heart, the alimentary canal is a simple straight tube to the anal open- 

 ing, which is not far from the end of the tail. The liver is large, and 

 consists of a broad, thick and short right lobe, which encloses the 

 pericardium with its broad, forward portion, and folds over the intes- 

 tinal canal; the left lobe is but slightly connected with the right, and 

 holds a median position below it, enclosing the intestinal canal on its 

 inner surface. The gall bladder is relatively large, and placed be- 

 tween the lobes of the liver. The heart is small, of the usual form 

 in fishes, and is enclosed in a pericardium. The cardiac aorta is 

 proportionally large, and gives off its branches alternately to the 

 six branchial sacs on each side. The branchial sacs are placed on 

 each side of the oesophagus, lying directly against its outer waifs, 

 and the water passes into them by a small pore opening directly 



1 Owen describes the organ of sight in the Lancelet and Myxine as " a minute 

 tegumentary follicle coated by dark pigment, which receives the end of a special 

 cerebral nerve." 



