88 



reticulated and the finer fasciculated kinds, which seem to partake of 

 both sorts. 



In the substances considered as alcyonia by Donati, as well as in 

 some of those which have been described by Count Marsilli, similar 

 large bundles of elastic fibres like needles were discovered. These had 

 been reckoned alcyonia by most authors, but in Mr. Ellis's opinion 

 they should not be so reckoned, since neither Donati nor Marsilli 

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

 sidering the existence of these as the distinguishing character of the 

 genus alcyonium, as much as the pores without the polypes in thesa 

 elastic fibrous bodies is the character of the sponges*. 



It is evident that these needle-like spiculse 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 spicules may of course be 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 alcyonia and 

 the sponges, even in a recent state, is considered, the oryctologist will 

 easily find an excuse for his inability, to make a similar distinction 

 between these substances, after they have undergone the lapidifying 

 process : when their pores have become filled ; and their colour and 

 their substance, and, in fact, their whole nature has been changed. 

 Indeed, the assumed generic difference between the alcyonia and 

 sponges is such as must be entirely lost in most of these substances 

 which have undergone the change of petrifaction. Whether the pores, 

 which are discoverable in a fossil, were the dwellings of the polypous 

 hydrae or not, can no longer be ascertained; since their radiation, 

 which is supposed to characterize the openings in which these minute 

 animals exist, and which is frequently so faint in the recent alcyonium 



* The Natural History of Zoophytes, &c. P. 183. 



