Annelids (Ringed Worms). ^y 



their hiding places ; and in some of the smallest kinds this sensitive- 

 ness goes so far, that they feel even the momentary darkening 

 of the tank caused by a cloud drifting across the face of the sun. 

 Tlie fact that the brilliant red gills of Protula become bleached 

 after some months in the Aquarium is probably also to be put 

 down to an effect of the hght. 



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 enchant- 

 ing 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. All these worms are fixed to 

 rocks or wood or have the lower part of the tube stuck into the 

 ground, and several species settle in such masses on the bottoms 

 of ships that their progress is considerably retarded. Not all 

 Tube-worms secrete calcareous shells or leathery ones, like 

 those mentioned above; some saturate the sand in which they 

 burrow with a slimy secretion from their skin and form in this 

 way delicate tubes of sand. Such are possessed by Arenicola, 

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

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

 tacles 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 encase themselves with mud, or form 

 long horny tubes, open at both ends and resembling the shaft of 

 a feather: Onuphis. 



All these animals, when young, are entirely differently con- 

 stituted. From the eggs issue free-swimming 

 larvse 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 f r e e - 

 living Annelids. The Bay of Naples 

 has long been celebrated among zoologists as 

 one of the richest localities for these worms. Fig. i6i. 



Still only a small portion are suitable for the Alciopa Cantrainii, 

 purposes of an Aquarium, as most of them live '2 nat. size, 



secluded in the mud or in the cracks of the 

 rocks. One of the finest is the Sea-mouse, Aphrodite (fig. 130), 

 the bristling coat of which reflects with a bright metalic lustre 

 all the colours of the rainbow. Its nearest relation is the very 

 common Hermione, which in spite of its beautiful name is a dis- 



