150 



NEREIDES. 



there are four prickles in each cluster of its dorsal mammillae ; the 

 anterior half has four many-prickled clusters in front, of an oblong 

 form ; three prickles in a line on a mesial lobe behind ; and oppo- 

 site, on the oral side, a cluster of several small prickles. The jaws 

 have ten obtuse denticulations ; but as those on the lower half are 

 not protuberant beyond the edge, it is not easy to ascertain the exact 

 number. 



I have seen specimens which were of a uniform grass-green colour, 

 tinted only with fuscous-brown about the head. At some seasons of 

 the year, in autumn especially, the body is often blotched with large 

 irregular yellow patches, and traversed with red lines, occasioned by 

 the viscera appearing through the skin. A red vessel may be always 

 traced down the middle of the back, giving off, to each foot, a small 

 branch, which is again slightly ramified ; and a similar vessel runs 

 along the flat ventral surface, which is marked with a median furrow. 

 But after being macerated in spirits (to which it communicates a 

 green colour), the colours entirely disappear, the worm becoming of 

 a uniform dead yellowish white, with a pearly gloss, most distinct on 

 the belly, and a tinge of brown sometimes remains on the back. 

 When allowed to die gradually in sea-water, the animal often pushes 

 forth its well-armed proboscis, which is marked with pale anastomo- 

 sing lines in a longitudinal direction, probably of a muscular cha- 

 racter. In dying it relaxes considerably. Fresh water is an imme- 

 diate poison to such individuals as are taken from the sea-shores ; 

 yet a partial mixture is not unfavourable to its habits, for the species 

 is to be found abundantly burrowing, like an earthworm, in mud in 

 the brackish water of our tide-ways and littoral marshes. 



To show how far the feet of the same species may vary, I have 



No. XXVI. — Nereis pelagica. 



given the above figures (No. XXVI.), — the three upper ones taken 

 from an individual immediately after being killed by immersion 

 in spirits, — the three lower ones from a specimen that had been pre- 

 served for some years. It would have been easy to have multi- 



