Annelids. 6* 



does not adhere to ist body. But not all T u b e - w o r m s secrete calca- 

 reous shells or leathery ones, like those mentioned above; some saturate 

 the sand in which th< y burrow with a slimy secretion from their skin and 

 form in this way delicate tubes of sand. Such are possessed by Areni- 

 cola. the lug-worm, so much used as bait in England. In the same man- 

 ner Terebella forms a dwelling , and its orange-coloured tentacles may 

 be seen protruding from the sand at the bottom of the tank . twisting 

 about in all directions in search of food. Others cement together small 

 stones, shells, and other similar objects (Shell-binders); while some encasr 

 themselves with mud, or form long horny tubes open at both ends and 

 resembling the shaft of a feather : Onuphis. This latter group crawl 

 about freely like the grub of the Caddisfly. while the palm-trees of 

 tank 22 fix themselves to rocks, woodwork , or other large objects , or 

 simply bury the lower end of their tube in the sand. Some kinds are a 

 veritable plague to navigation, accumulating in such masses on the keels 

 of ships that they retard their progress. 



All these animals, when young . are entirely differently constituted. 

 From the eggs issue free-swimming larvae of very curious form . which 

 after a while fix themselves to stones or weeds, and then by a complete 

 metamorphosis change into the worm-like animal and encase themselves 

 with a tube. 



Besides these tube-inhabiting Annelids, of which all the warmer seas 

 possess a variety of beautifully coloured kinds, there is a second group, 

 no less rich and varied: the free-living Annelids. 



The Bay of Naples has long been celebrated among zoologists as 

 one of the richest localities for these worms, and already up to the pre- 

 sent date (including the tube-inhabiting worms) about 300 different species 

 have been described. Still only a sm?ll portion 

 are suitable for the purposes of an Aquarium, 

 as most of them live secluded in the mud or in 

 the cracks of the rocks. One of the finest is the 

 Sea-mouse, Aphrodite (Fig. 123), the bristling 

 coat of which reflects with a bright metaDic lu- 

 stre all the colours of the rainbow. 



Its nearest relation is the very common 

 Hermione- which in spite of its beautiful name 

 is a disgusting animal , the hooked spines of 

 which penetrate into the hand that touches them, 

 and cause inflammation. Alciopa (Fig. 161) is as 

 transparent as the jelly-fish and other pelagic 

 animals, and like them lives near the surface of 

 the sea. It is rarely seen in the Aquarium (Tank 



Nr. 20), since the capture of such animals, as already mentioned, depends 

 much upon the weather (see p. 62, foot-note). 



