178 SABELLA. 



the advancing tube reaches the side of a glass cylinder. They then con- 

 tinue alike industrious, but frequently, as if to economise labour, the grow- 

 ing edifice is reduced to the segment of a cylinder, the transparent glass 

 supplying the defective portion. Whatever passes within is thus suffi- 

 ciently exposed. 



A Sabella previously carrying on its operations in a watch-glass, 

 will sometimes avail itself of the transparent side of a jar on coming in 

 contact with it. 



Some outstrip their neighbours. One working from below carries 

 its perfect cylinder to the surface of the sand, where it appears surround- 

 ed by a groove, occasioned by removal of the materials to raise the edge of 

 the dwelling. Should several tubes be covered during some time by sand, 

 a perfect labyrinth will be found on washing it out, from the labour of the 

 architects. 



The greatest activity is displayed during the warmest weather. 



These animals quit their tubes when the water becomes vitiated. 

 They survive a long time though divested of them, which they seem to do 

 spontaneously on other occasions. 



Their food is unknown. 



Specimens have lived thirteen months in confinement, therefore they 

 may be readily preserved. 



PLATE XXV. 



FIG. 1. Sabella alreolaria. 



2. Tentacular organs, enlarged. 



3. Ova, enlarged. 



4. Ova, more enlarged. 



2. SABELLA BELGICA AMPHITRITE AURICOMA. Plate XXV. Figs. 5, G. 



Lamarck proposes to institute a genus named Pcctinaria, compre- 

 hending certain species of marine animals, such as the preceding, with 

 others of its kind, and the subject of the present paragraph. 



I do not obviously see, however, that the former can be properly in- 

 cluded, from wanting such peculiar characters as belong very prominently 



