SERPUL^E. 419 



If a tolerably powerful glass can be brought within the neces- 

 sary focal distance, it will be seen that the exterior of the gill- 

 tufts is covered with wonderfully delicate filaments, or cilia, as 

 they are technically named, which are continually waving in reg- 

 ular ripples. Their movement constitutes a sharp current of 

 water, which not only washes against the gills and furnishes the 

 requisite supply of air for the regeneration of the blood, but car- 

 ries the water downward into the mouth, which opens at the bot- 

 tom of the gill-tufts. In the water is always a bountiful supply of 

 minute animal organisms, together with other substances, which, 

 although microscopically small, are in the aggregate sufficient to 

 feed the Serpula. This current is kept continually flowing as 

 long as the tentacles are protruded, and thus the creature is en- 

 abled to breathe, is supplied with nourishment, and the tube is 

 kept clean by the water current which is perpetually rushing 

 through it. . 



We now come to that wonderful portion of the animal which 

 is called by naturalists the "operculum," and which is popularly 

 and rightly known as the "stopper." This is the conical ap- 

 pendage which hangs from the tube, and is used in closing its 

 mouth when the gills have been withdrawn. The operculum is 

 known to be a development of one of the antenna?, the other an- 

 tenna being small, slender, and without any such appendage. To 

 systematic naturalists the operculum is one of the most valuable 

 parts of the animal, as it is often found in the tube in good pres- 

 ervation long after all the softer parts of the animal have disap- 

 peared. We can learn but little from the tube, as it is very sim- 

 ilar in animals belonging to different genera. The value of the 

 operculum was detected by Dr. Philippi, and has been corrobo- 

 rated by Dr. Baird, who has made great use of it in some valua- 

 ble papers on specimens of Serpula? which are now in the British 

 Museum. 



In one genus, Eupomatus, for instance, the operculum is fur- 

 nished with a number of movable spikes. In one species, Eupo- 

 matus Boltoni, these spikes are about twenty in number, and are 

 hard, flat, and calcareous. Their form is very much like that of 

 a hedger's bill-hook, except that they are furnished in the inner 

 edge with several bold tooth-like projections. These spikes are 

 called by Philippi horns or cornua, and are always deeply toothed, 

 whatever may be the species. The very appropriate name, Eu- 

 pomatus, is formed from two Greek words, and signifies "beauti- 



