148 NEREIS. 



The whole creature is white to the eye, unless a small portion about 

 the head. 



It is restless and active, so as to render microscopical observations 

 extremely difficult, and hence the crescent-shaped eye may consist of 

 specks. 



One seemed to have grown somewhat large in two or three months. 



PLATE XX. 



FIG. 23. Nereis parva. 



24. Head, enlarged. 



25. Posterior extremity, enlarged. 



6. NEREIS ARIES. Ram's Horn Nereis. Plate XX. Figs. 3, 4, 5, 6. 



Length between two and three inches. Body composed of numerous 

 segments, with a row of pencils on each side. Anterior extremity ter- 

 minating in a stout projection, forked ; posterior extremity terminating 

 in eight or nine stout prongs surrounding the vent. Two fleshy, recurving, 

 flexible antennsB almost constantly preserve a position resembling ram's 

 horns. The general aspect of the animal is reddish ; a red vessel inter- 

 nally traversing the body. 



It swims through the water by contortions, and its motions are 

 sometimes so violent as to rend the body asunder. Also, it involves it- 

 self in a knot, and forms a rude covering of sand. 



PLATE 



FIG. 3. Nereis aries, enlarged, from a specimen eighteen lines long. 



4. Anterior portion, upper, surface, enlarged. 



5. Anterior under surface, enlarged. 



6. Posterior extremity, enlarged. 



7. NEREIS REMEX, PHYLLODOCIA LAMINOSA. Plate XXIII. Figs. 1, 2, 



3, 4, 5, 6, 7. 



This animal is one of the few which it seems impossible to recognize 

 under the various nomenclature which has embroiled the genus Nereis. 



