116 THE SEA PEN. 



general mass, seems to be unperceived, or unfelt at 

 a remote portion ; but a general shock being given, 

 the whole mass, and the polyps, contract together. 



Cuvier regards the sea-pens as forming a distinct 

 section, and terms them swimming, or detached 

 polyps. 



A SEA PEN. PENNATULA. 



These animals, however, have a calcareous axis, 

 though not fixed. Their name is derived from 

 their resemblance to a quill feather, a double set of 

 branches, occupying both sides of a shaft. Each 

 branch is furnished with a row of polyps, resembling 

 the barbules along the filaments, or barbs, com- 

 posing the vane of a quill. 



POLYPS OP A BARB OF THE SEA-PEN. 



Almost endless is the variety of form which the 

 fixed zoophytes exhibit, in the warmer latitudes of 

 the ocean ; affording abundant employment for the 



