GEMICELLAEIA. 179 



dren on the sea-coast, after a gale of wind has cast up 

 treasures of the deep within our reach. It belongs to a family 

 (Plumularia) which has several species, but none so beautiful 

 as this. We find it twined round the stems and pods of 

 Halidrys siliquosa ; sometimes a mussel-shell will have a 

 feathery plume upon its rich blue surface, and tens of thou- 

 sands of tiny creatures spring forth from those sessile cups, 

 ranged all along the pinna3 ; they are shaped somewhat like 

 lilies of the valley, with a projecting spine beneath each, and 

 the vesicles are oblong, pod-like, and banded with cristated 

 ribs; the more of these, the better the specimen; but it 

 should be examined when fresh, and is more easily found^ 

 perhaps, than any other zoophyte. 



PLUMULAEIA FALCATA, 



is another species, in which you may observe the polype 

 cells seated in close array along the pinna? of the branches ; 

 these, when dry, bend inwards like a sickle, and give the 

 name of Sickle Coralline to this zoophyte. It is dredged 

 in deep water and common on oyster beds. A wavy branch 

 of it will not unfrequently be found on the back of some old 

 crab, which has served as its perambulator, and carried it 

 into rich stores of Diatoms and Infusoria, such as it 

 delights in. 



P O L Y Z O A. 



GEMICELLAEIA. 



This is one of the Polyzoa, more highly organized than 

 Sertularia, &c., and therefore ranking considerably higher 

 in the scale of creation. The difference in the skeleton 

 here prepared is, that we have a calcareous cell instead of a 

 horny one. Almost all the Polyzoa have calcareous sheaths, 

 or polyzoaries, as this skeleton is called, instead of polypi- 

 dom, which belongs to the lower class of zoophytes. The. 

 difference between the two is this : a polypidom is a sepat- 

 rate horny case, which is formed before the indwelling and! 

 connected polype, and the polype itself is part of a common 



