MARINE WORMS 185 



appearance of a whitish fungoid growth round the mouth of what 

 appears to be an empty tube ; and if, through neglect, the water of 

 the aquarium has been allowed to become contaminated by the 

 products of decomposition, it will often happen that some of the 

 living worms will come entirely out from their tubes, as if to seek a 

 more sanitary situation. Thus, the exit of worms from their homes 

 may always be looked upon as pointing to a suspicious condition 

 of the water which, if not corrected immediately, may lead to the 

 death of all. 



The species we have briefly described is by far the commonest 

 of the genus Sabella, but there are several others to be found on our 

 shores. Some are of a solitary nature, and construct a sandy tube 

 so much like that of a certain species of Terebella that they may be 

 mistaken for that genus. Another solitary species builds a hard 

 stony tube of carbonate of lime that has been extracted from the 

 sea water ; and although it is hardly 

 possible to take the live worm from 

 this calcareous tube without injury, 

 the animal may be obtained intact 

 for examination or preservation by 

 dissolving away the tube in dilute 

 hydrochloric acid. 



While engaged in collecting 

 specimens on the sea shore we are F IO . 121. A TUBE OP Serpula 

 continually meeting with stones ATTACHED TO A SHELL 



and shells that are more or less 



covered with white, limy tubes twisted into all manner of serpentine 

 forms. These are the tubes of other marine worms known as the 

 Serpulce, which, like the species previously mentioned, are inter- 

 esting objects for the aquarium. 



The tubes themselves are worthy of study and preservation, 

 more especially as they vary in form, and may, to some extent, 

 provide a means by which the different species may be identified. 

 They are composed of fine layers of calcareous matter secreted by 

 the body of the worm within, and lined by a thin leathery membrane 

 which may be easily exposed by dissolving away the mineral 

 matter as just described. Some are triangular in section, and often 

 distinctly keeled, while others are cylindrical, and flattened more 

 or less on the lower side. The triangular tubes are attached to 

 stones or shells throughout their length, but the cylindrical ones are 

 often elevated above the surface in the wider and newer part. 



