Miscellanea Zoologica. 529 



there is a distinct interval between the dorsal and caudal fins ; the 

 tail is margined with white ; the anal and dorsal fins are marked 

 with six or seven blackish spots, which extend beyond the base of the 

 rays, towards the body of the fish ; and its shape is of an oblong 

 form. None of these characters apply to the Monochirus minutus. 

 ( To be continued.) 



IV. — Miscellanea Zoologica. By George Johnston, M.D., Fel- 

 low of the Royal College of Surgeons of Edinburgh. Plates XVII. 

 XVII I. (Continued from p. 382.) 



II A Description of some Planarian Worms. 



Class ENTOZOA, RudolphL— VERMES, Lamarck. 



Order Sterelmintha, Owen — V. molles, Lamarck. 



Family Planulariae, Lamarck. 



Genus Nemertes,* Johnston. 



Character. — Body linear-elongate, contractile, somewhat com- 

 pressed, soft, even and continuous : anterior extremity mostly with 

 several ocellifonn points, and two occipital approximate spots mark- 

 ing the position of a double centre of circulation : mouth a simple ter- 

 minal pore : anus terminal. 



Obs. — The worms which I include in this genus are of a linear 

 form and very contractile, so that when extended in the act of mov- 

 ing through the water or mud, they exceed their length when at 

 rest by three, four, or more measures. They are soft and glutinous, 

 but with more firmness of structure than their appearance indicates; 

 and to the naked eye they are perfectly smooth, exhibiting no trace 

 of articulations or wrinkles, though when contracted and viewed 

 through a magnifier, we find that the margins are minutely crenu- 

 late. The anterior extremity is usually marked by several black 

 specks arranged on each side of it, variable in number according to 

 the species, and which are considered by Muller and others as or- 

 gans of vision. We are not able, with our small microscope, to 

 discover any peculiar organization in them, yet there is reason, (not- 

 withstanding the objection of Lamarck, founded on the want of op- 

 tic nerves and a nervous system, t) to assent in this opinion, from 



* Nemertes — one of the Nereides. — The genus so named by Cuvier (Reg. 

 Anim. iii. p. 259,) for the reception of the sea Long- worm of Borlase, had been 

 previously named Lineus by Sowerby ; and Cuvier's name being thus unneces- 

 sary, I have thought myself warranted in taking it as the designation of some 

 worms nearly allied to Lineus, but which are certainly generically distinct. 



f Hist. Nat. des Anim. s. Vert. iii. p. 177. 



