POLYCELETA OF THE L.M.B.C. DISTRICT. 243 



N. fucata is sometimes taken free. Such specimens, 

 as well as those forcibly taken from their refuge in shells, 

 display a very peculiar mode of swimming. Turning on 

 their side they assume the outline of an S much drawn 

 out, and move through the water with a gentle undulat- 

 ing shivering motion with a weakness suggesting want of 

 training, and without any of the vigorous lashing seen in 

 Nephthijs and in Nereis virens, N. pelagica, &c. These 

 latter swim upon the ventral surface of the body. Used 

 for bait sometimes by the Manx fishermen. 



* Nereis (Alitta) virens, Sars. 



Hab: E, KB. 



Abundant between tide-marks along the Mersey shore 

 from Egremont to New Brighton, burrowing in patches of 

 very stony boulder clay. Its extensive burrows are 

 mucus lined. This mucus is secreted by enormous 

 numbers of tubules found along the dorsum and in the 

 lobes of the feet, especially in the great leaf-like upper 

 lobe of the notopodium, the so-called " branchia " of 

 Kinberg. This lobe seems pre-eminently modified to act 

 as a great secretive organ, its great expanse and lamellar 

 form giving the maximum of available surface while occu- 

 pying the minimum of room. Each is richly supplied 

 with blood vessels and its substance is crowded with 

 masses of tubuli opening on the surface. The cirri (dorsal 

 and ventral) contain no tubules. Immense quantity of 

 mucus is thrown off very rapidly after capture, so filthy 

 and dense that it is difficult to make out the presence of 

 the worms at all. 



N. virens (the N. Yankiana of Quatrefages) is the most 

 esteemed of bait worms in this district. The fishermen 

 have given it the name of "Creeper." 



