THE SILKWORM AND THE FAN AMPHITRITE. 429 



are remarkable for the transparency of their newly-constructed 

 dwellings. Of these, a very singular example is found in the 

 Silkworm Amphitrite {Amphitrite bombyx). 



The reader will remember that one, at least, of the Terebella? 

 can make a structure which is as transparent as isinglass, and will 

 not, therefore, be surprised to find that another annelid possesses 

 similar powers. The tube of the Silkworm Amphitrite is longer 

 than the body, and is made entirely of the gelatinous secretion 

 which in most of the species is used as a cement for fastening to- 

 gether the sand, shells, mud, and other materials of which the tube 

 is formed. In this creature, however, the secretion is so plentiful 

 that it forms the whole of the tube. 



Nor does it content itself with a single tube, but forms several, 

 one after the other. When first made, the tube is so beautifully 

 transparent that the body of the inhabitant can be seen almost as 

 plainly as through glass ; but in process of time it becomes in- 

 crusted with mud and sand, and almost looks as if it were made 

 of very dirty leather. The average length of an adult specimen 

 is three inches, and its beautiful gill-fan is decorated with brown 

 and yellow. As is the case with most of the tube-inhabiting 

 worms, it is a very timid creature, jerking itself into the tube on 

 the least alarm, and contracting the orifice after it has retired into 

 seclusion. 



Another species, the Fan Amphitrite {Amphitrite ventila- 

 brum), forms a long and tough tube, which is apparently made of 

 shoe-leather, but which is really formed from mud and the cement 

 which is secreted by the animal. Mr. Bymer Jones has very lu- 

 cidly described the mode of construction: "We will suppose a 

 specimen, with its plume fully expanded, in a jar filled with its 

 native element. In this condition, if a drop of liquid mud be 

 dropped from above into the water so as to disturb its cleanliness, 

 the animal immediately begins to arouse itself, and all the thou- 

 sands of cilia that fringe its branchial plumules are discovered to 

 be in vigorous activity, collecting by their incessant action the 

 diffused muddy particles into a loose mass, which is soon per- 

 ceived visibly accumulating in the bottom of the funnel. Mean- 

 time the neck, or first segment of the body, rising unusually high 

 above the orifice of the tube, exhibits two fleshy lobes or trowels, 

 beating down the thin edges as they fold and clasp over the mar- 

 gin, like our fingers pressing a flattened cake against the palm of 

 the hand. 



