Annelids. 67 





In the sea we may often see a natural garden of this kind; looked 

 at through the clear water of a rocky coast it is an enchanting sight, 

 and always yields a rich harvest to the naturalist, not only of these 

 worms, but of many other animals which have taken up their abode 

 amongst them. The tube is merely a house formed by the worm, and 

 does not adhere to its body. But not all Tube-worms secrete cal- 

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

 the sand in which they burrow with a slimy secretion of their skin and 

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

 nicola, the lug-worm, so much used as bait in England; in the same 

 manner Terebella forms a dwelling, and its orange-coloured tentacles 

 may be seen protruding from the sand at the bottom of the tank, twist- 

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

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

 encase 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 in 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 forms, 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 richest localities for these worms, and up to the present date 

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

 have been described. Still only a small 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, Aphrodita (Fig. 123), the 

 bristling coat of which reflects with a bright 

 metallic lustre 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. 162) is 

 as transparent as the jelly-fish and other pelagic Fig.162. Alciopa Cantrainii, 

 forms, and like them lives near the surface of */ 2 na t- size, 



the sea. It is rarely seen in the Aquarium 



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

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



5* 



