34 MARINE WORMS. 



and Jersey on the other. There we throw over the dredge, 

 and when it is soon hauled in, most conspicuous of the trea- 

 sures brought up are numerous fine examples of that most 

 beautiful of the heart-urchins — the purple Spatangus (S. 

 purpureus). Each of these we eagerly search with shrewd 

 idea of the result. Yes, there on the underside, clinging, flat 

 and close to the test, or maybe wriggled among the spines, is 

 a pretty inch-long scale-worm, Polynoe castanea. So far I 

 have never found this worm elsewhere than in company with 

 Spatangus; generally in a position close to the mouth, the 

 number upon each host being limited to a single individual. 

 This little worm is extremely beautiful ; the fifteen pairs of 

 scales (elytra) which cover the back like so many pairs of 

 dainty-hued tiles are coloured on the exposed parts a rich 

 lavender-purple, so closely approximating in colour to that of 

 the host that an unpractised eye may well be excused if it be 

 overlooked. In spirit the colour fades to a madder-brown. 



Upon the irritation of being roughly handled or that 

 which follows immersion in spirit, this animal, like so many of 

 its relatives, immediately breaks up into pieces — a habit un- 

 doubtedly acquired with the view and in the hope that the 

 portion remaining with the head may escape to a place of 

 safety in the confusion ensuing ; when, too, the attention of 

 the foe may be occupied with the devouring of the worthless 

 though still wriggling hinder parts of the body. The powers 

 of recuperation in these worms are very great and the loss of 

 a feAV of the hinder segments of the body is of trifling moment. 

 But to return from this digression. In most of the Pohjnoince 

 the rupturing of the body under the influence of danger or 

 irritation may take place indefinitely at almost any segment 

 of the body. Polynoe castanea is, however, curiously charac- 

 terised by the fact that the severance very generally takes 

 place at one particular region — just about one-fifth of the 

 length of the body from the head. Sometimes in those thrown 

 into spirit the animal dies just after the body wall has divided 

 and before any corresponding rent has occurred in the thick 

 wall of the alimentary canal. In these latter cases the severed 

 ends of the body wall shrink widely apart, giving a grotesque 

 appearance of one small worm linked to a long one by a stout 

 fleshy bar. 



Beyond the comparative security enjoyed by living among 

 the spines of such an unappetising creature as Spatangus — the 

 habitat is probably attractive to the commensal worm by 

 reason of the multitude of tiny crustaceans which also seek 

 hiding places among the spines of the urchin. Then again 



