FOSSIL ALCYONIA. 4$ 



be fo reckoned, since neither Donati nor Marsilli mentions 

 any polype suckers extending out of their pores ; he con- 

 sidering the exiftence of thefe as the distinguishing cha- , 

 racter of the genus alcyonium, as much as the pores with- 

 out the polypes in these elastic fibrous bodies is the charac- 

 ter of the sponges *. 



It is evident that these needle-like spiculoe cannot be 

 considered as belonging to the genus spongia only ; since 

 among the alcyonia some are admitted to be formed of a 

 spongy substance, into the composition of which these spi- 

 cules may of course Ije expected to enter ; on the presence 

 or absence therefore of polypes in the cells of the substance 

 must alone depend the necessary distinction. 



But when the difficulty of distinguishing between the Most difficult 

 alcyonia and the sponges, even in a recent state, is consi- m the foss ^ 

 dered, the oryctologist wjll easily rind an excuse for his in- 

 ability, to make a similar diftinction between these sub- 

 stances, after they have undergone the lapidifying process : 

 when their pores have become filled ; and their colour and 

 their subftance, and, in fact, their whole nature has been 

 changed. Indeed, the assumed generic difference between 

 the alcyonia and sponges is such as mull be entirely loft in 

 mod of these substances which have undergone the change 

 of petrifaction. Whetjier the pores, which are discoverable 

 in a fossil, were the dwelling of the polypous hydraeornot, 

 can no longer be ascertained ; since their radiation, which 

 is supposed to characterize the openings in which these mi- 

 nute animals exist, and which is frequently so faint in the 

 recent alcyonium as hardly to be detected, is very likely, in 

 the fossil substance, to be still more difficult to be made 

 out. Indeed, from this indistinctness of the radiation, 

 much difficulty appears to have arisen in making the neces- 

 sary distinction between even the recent sponges and al- 

 cyonia ; the graduation from the perfectly radiated opening 

 of the alcyonium, to the plain opening of the sponge, 

 being so gradual and imperceptible, as to render it a dif- 

 ficult task, even where the substances are in a recent state, 

 to draw the line where alcyonium ceases and sponge begins. 



* The Natural History of Zoophytes, &c. p. 163. 



But 



