IOO 



NEMERTINEA 



CHAP. 



Nemertines for the most part closely resemble one another in 

 all essential points, though they differ considerably in size, 

 colour, and external details. They vary in length from less 

 than an inch to thirty yards, this 

 extreme size being attained by 

 Linens marinus. 



Nemertines are common on the 

 British coasts ; about forty species 

 have been recorded from this area. 

 On turning over a stone on a sandy 

 or muddy. shore in a pool left by 



the receding tide, 



there may often 



be seen a coiled 



mass, having the 



appearance of a 



uniform slimy 



string twisted 



into a compli- 

 cated knot. If 



it be carefully 



removed, the 



ends can gener- 

 ally be made 



out, one bluntly 



Fig. 48. Lineus mar 

 inus Mont., from the 



living specimen in rounded and the 



the coiled condition. ^1. . qlio-htlv 



Plymouth, x 1 

 Anterior end ; 

 posterior end. 



other 

 by tapering (Fig. 



48, a and b). Oc- 

 casionally there may be seen attached 

 to the blunter end a fine thread, 

 which moves about freely. This 

 thread may, by an instantaneous 

 movement, be drawn into the body, 

 no trace of its existence being left 

 except at the tip of the head, 

 where a small pore is visible ; this 

 is the orifice through which it was 

 withdrawn. Shortly afterwards the thread may be again shot 

 out, the process being instantaneous and often accomplished with 



Fig. 49. L. marinus, from the same 

 specimen as Fig. 48, in the 

 expanded condition, a, Anterior 

 end ; b, posterior end. 



