SEA-WORMS. 121 



is brought into play by a special set of muscles, so soon 

 as the combatants are sufficiently near to grapple in close 

 fight." 



From the use of the word " feet " in the foregoing it must 

 not be inferred that worms have true jointed feet, like those 

 of crabs or insects, for instance. What are sometimes spoken 

 of as feet in the case of the worm-class are lateral warts, 

 which carry glassy and elastic bristles in little bundles, like 

 paint brushes ; and these are partially withdrawn into a sheath, 

 or pushed out and used like oars with a rowing motion that, 

 all moving rhythmically, send the creature along very speedily, 

 especially when burrowing in sand or mud. To such of my 

 readers as possess a microscope I would advise the careful 

 examination of these bristles, their variety of form, as men- 

 tioned by M. Quatrefages, will afford subjects for considerable 

 study ; though it is open to doubt whether they are ever used 

 for offensive or defensive purposes. 



There is a family of these Sea-worms whose members are 

 mostly characterised by the possession of broad overlapping 

 scales upon their backs, and beneath these are the rudimentary 

 gills, the plates being evidently intended to create currents to 

 supply the blood with oxygen. Two of the most-likely-to-be- 

 met-with of these are Polynoe squamata and P. cirrata. The 

 former is uniformly pale-brown on the upper side, completely 

 clothed with the large, loose-looking scales, beyond which the 

 three pairs of tentacles, and the lateral organs of touch (cirri) 

 project. It is not easy to examine this creature closely whilst 

 it is in a living condition, it is so sensitive to the light, and 

 ever seeking to avoid it. Its chief concern is, " where can I 

 hide ? " It possesses four eyes, and its scales are delicately 

 fringed. Polyno; cirrata is larger, darker, and its feet pro- 

 trude further beyond the edge of the scales. 



The Sea-mouse (Aphrodita actileatd) belongs to this section. 

 It is a species that prefers deeper water, but sometimes comes 

 to shore with a heavy sea. In addition to its scales the arched 



