ESCHARS. 421 



hole, were sprouted out four small, transparent straw- 

 coloured thorns, which seemed to protect and cover 

 those cavities." It would be difficult to improve 

 upon a description so simple and so graphic. 



The ESCHARS are very nearly allied to the Flustrae 

 in their general structure, the principal difference 

 between the two consisting in the nature of their 

 skeleton or polypidom, which in the Escharae is solidi- 

 fied by the deposit of calcareous earth in its sub- 

 stance, until it assumes a stony hardness, instead of 

 remaining soft and flexible, as in Flustra. In both 

 races the individual cells vary in shape in different 

 species, and generally have their orifices defended by 

 projecting spines, or sometimes by a moveable oper- 

 culum or lid, which apparently answers the same pur- 

 pose as the setae of Bowerbankia, described in the last 

 chapter, by defending the entrance to the cell. 



Let not the reader suppose, however, that the pre- 

 cise and elegant structure of the surface of these Sea- 

 mats is all that they present worthy of a naturalist's 

 admiration ; or that to pick them up as they lie dis- 

 carded on the beach 



" Like ocean-weeds heap'd on the surf-beaten shore " 



is the proper way to obtain them for microscopical 

 examination : they must be sought for in their living 

 state far out at sea, or at the very lowest tides, grow- 

 ing upon their native rocks, incrusting shells, or 

 spreading out upon the stems and fronds of Fuci. 

 Thus procured, and kept in glasses filled with fresh 

 sea-water, it is easy to observe the wondrous spectacle 

 they offer for our contemplation : thousands of Polyp- 



