128 THE TORE AD-HORNED SPIO. 



Although grains of sand, small pebbles, and shells, or frag- 

 ments of shells, are the materials usually employed in the 

 formation of the tube, the Terebella is by no means indisposed 

 to make use of other substances when they come to hand ; and in 

 one of these tubes now before us, the spine of an echinus, several 

 fragments of sea-weed, and even small portions of wood, have all 

 been worked into the structure. 



We can say nothing as to the behaviour of the Terebella in 

 the Aquarium, having no experience of it in confinement ; but we 

 have somewhere seen it stated that with care it may be kept 

 alive for a considerable period, and that by skilfully managing 

 the supplying of materials, it may be got to construct its tube in 

 bands of various colours. 



One of the most minute of these tube-making worms is the little 

 Spio ceticornis, which may be found in abundance on old shells, 

 and is sure to turn up, if looked for, in any long-established 

 Aquarium. It derives its name from the two long thread-like 

 tentacles, which protrude from the mouth of the tube, and are 

 kept in almost constant motion. The Spio is quite of a social 

 turn, and usually occurs in colonies of several individuals ; and 

 when they are all in full play, twirling about their tentacles 

 together, they make quite a commotion on a small scale. 



These little worms are large enough to be seen in a good light 

 quite plainly with the naked eye, but when viewed through a 

 glass, they have an extremely interesting appearance. The tubes, 

 which stand erect for a good part of their length, are seen to be 

 formed of minute particles of sand and dirt, and terminate in a 

 circular orifice, from which the worms protrude their two long 

 and almost translucent tentacles. The movements of these 

 tentacles are somewhat peculiar ; at one movement they are 

 seen almost erect and but slightly divergent, then one of them 

 suddenly contracts itself with a singular quirk, and makes a 

 flourish at right angles to its fellow, crinkling and twisting 

 in all sorts of curves as it goes ; meanwhile the other tentacle 

 is twitching and jerking itself as it still stands upright, and then, 

 bending down, it joins the first, and the pair sweep through the 

 water together, outstretched to their full extent, when they stand 

 erect again, to twitch and twirl about as before. 



But what has more particularly interested us in watching the 

 movements of this tiny animal, is the singular power which it 



