New Species of Sti cHebacJc. 



The pulsation of the heart, seen immediately in front of the yolk- 

 bag, and the movement of the blood in the ressels of the yolk- 

 bag, in the aorta and the large veins above and below the spinal 

 column, as well as in the transverse branches passing between the 

 muscular flakes of the sides, can be very distinctly perceived. 

 The spinal column appears as a uniform cartilaginous hyaline 

 cord, and the pectoral fins are fully developed and in constant 

 motion. The posterior part of the body is surrounded by a deli- 

 cate membranous fin, terminating in a rounded point at the tail. 



As the yolk bag diminishes in size, beautiful stellate pigment 

 cells become developed in the skin, and render it too opaque to 

 permit the interior structures to be well seen ; and before the 

 little creature has attained the length of one-sixth of an inch, it 

 has all the appearance of the adult, and may be seen slowly 

 swimming or hovering, with its bright eyes rolling in search of 

 the minute crustaceans, worms, rotifers and animalcules which 

 form its prey, and which it seizes by sudden, quick darts. When 

 alarmed, it hides under stones or algae, or remains motionless 

 over some part of the bottom resembling its own colour, which, 

 when it is irritated or frightened, deepens almost in!o black. 



The fry remain in the brooks throughout the spring and early 

 summer ; but the greater part disappear, descending I suppose 

 into the river, before autumn. Those that remain are now 

 (September) nearly an inch in length, and will probably be full- 

 grown next spring. 



The following is the description of the adult in spring : — 



Length, two inches ; heal to body, as 1 to 4 ; depth of body 

 to length, as 1 to 4. Form, compressed, especially above; back, 

 regularly arched to the end of the dorsal fin, from which it curves 

 upward slightly to the insertion of the caudal fin. Head, regularly 

 conical, obliquely truncated by the lower jaw. Eye, prominent, 

 diameter one-tenth of an inch. Nostril, half-way between eye and 

 pre-maxillary, and on a level with the upper part of the orbit. 

 Body, quite destitute of bony plates; on this last character, the 

 absence of defensive armour, I have given it the specific name 

 gymnetes. Pre-operculum, bent nearly at a right angle, rounded 

 at apex. Operculum, rounded below, nearly straight above, 

 rounded at superior posterior angle. Brancheostegal rays, three. 

 Mucous pores, three above each eye, a few very small under the 

 eye ; on the occiput a curved row of pores convex backward ; at 

 the edge of the operculum two less distinct rows convex upward. 



