320 THE BRITISH NATURE BOOK 



manner by means of their trowel-like antennae. The Sabellae breathe by means 

 of a beautiful plume of feathered gills protruding from their sand-tubes. 



The Serpula makes the limy white tubes often found on stones and old 

 shells, and has an exquisite plume of red or scarlet gills, to be seen if the stone 

 is placed in a glass of salt water. It also possesses tufts of bristles, by which 

 it moves up and down its tube ; but it can vanish within with a suddenness 

 which is almost startling. This is due to a row of hooked teeth on its back, 

 13,000 odd in number. 



Notice the curious stopper-like organ (a modified tentacle) by which the 

 Serpula blocks the entrance to its home. There are several species to be found. 



The Spirorbis is very like the Serpula, but coils its tube in a flat spiral. 

 It is exceedingly common on stones and weeds. 



The Terebella (Terebella figulus) is some 4 inches long, and makes a tube 

 covered with grains of sand of a tough and almost leathery consistency. The 

 Shellbinder (T. littoralis) uses particles of broken shells instead of sand. 



The Nemertes, or LONG-WORM (Nemertes borlasii, now known as Lineus 

 marinus), is a most curious creature, found beneath stones, and looking like 

 a twisted bootlace coiled and tangled and of remarkable length. It can 

 stretch itself also like a piece of elastic a trick which it plays in capturing 

 its prey, which it holds with its sucker-like mouth and interior beak. It then 

 proceeds to " play " its victim as a fly-fisher plays a trout, stretching itself 

 out and then retracting its length until the victim is exhausted. 



The Nereis (LEAF-WORM) is a common seaside worm, some species being 

 of great length. It is a favourite worm for bait, and may be found under 

 stones and in muddy sand. Its head is conical, with several antennse ; its 

 colour brown, with a red line down the back, and in sunlight a blue iridescence 

 plays over the skin. The under side is pink. It has well-developed feet 

 400 pairs ! 



Of such are .the Wilfry (Nereis pelagica), fleshy fawn-coloured (6-8 

 inches) ; the Pearly Nere'is (Nephthys margaritacea) , much smaller ; the 

 Rainbow Nereis (Phyllodoce lamelligera). 



The Sea Mouse (Aphrodita aculeata), 3 or 4 inches long, is like a slug covered 

 with matted bristles, and usually very dirty ; but when washed in clear water 

 it is a beautiful object, glowing with many iridescent colours. The bristles 

 act as a sort of filter, purifying the water that enters the gills. In addition, 

 they have barbed tips and saw-like edges, and so serve as a means of defence. 

 The bristles, however, are too weak to pierce the hands. 



Leeches. These worm-like animals have no bristles or feet, but ringed 

 and extensile bodies, with a sucker at the tail and a strong sucking mouth. 

 Several varieties inhabit both salt and fresh water, the marine species being 

 found on fish. 



The Medicinal Leech (Hirudo medicinalis) was once far more largely used 

 than it is to-day in blood-letting. It has a greenish black body, 2 or 3 

 inches long, and broken yellow bands and spots on the back. It possesses 



