THE LYTHOPHYTtS AND SPONGES. 425 



mically, they all discover tlie marks of animal formation ; the 

 corals, as was said, dissolve in acids, the sponges burn with an 

 odour strongly resembling that of burnt horn. We are left some- 

 what at a loss with regard to the precise manner in which this 



The Pencil Coralline. — This coralline varies in the thickness of its 

 branches, as well as in its size ; they are found from one inch to four inches 

 long ; in some the stem is very short, in others it is four times as long as 

 the head. They are generally white. The joints are easily distinguished, 

 wliere the branches divide ; the stem is composed of tubular iilaments, 

 covered with a calcarious crust. They adhere to shells by the base of these 

 filaments, and are often found iu the West Indian ocean, growing to shells, 

 many of them together. 



The Mop Coralline. — This coralline has a single membranaceous wrinkled 

 stem, on the top of which is a tuft of jointed dichotomous branches. This 

 is the most singular of all this genus, and differs from the rest by the regu- 

 lar wrinkles of the stem, which is small at the base, and grows wider as it 

 rises, till it sends forth its branches at the top : from the base it sends forth 

 branched tubes, like the sertularias, by which it adheres : these tubes do 

 not lessen as they extend, but have an equal diameter their whole length. 

 Wlieu the branches at the top are magnified, their calcarious crust, full of 

 pores, may be distinguished, which brings it to this genus. Tliis is found iu 

 the American seas, many growing together, particularly near the Bahama 

 Islands. 



The Sertularia, or Sea Pen, is a many-headed animal, growing in the 

 shape of a plant, and fixed by its base. Its tubulous homy stem is full of 

 cup-shaped denticles, through which proceed little heads, in the form of 

 polypes, from the gelatinous medullary part which is continued through the 

 inside. Nature has been very favourable to the animals of this genus, in 

 providing little cup-like denticles to secure their many tender heads safe, 

 when they are drawn in upon any alarm of danger ; whereas the heads of 

 the tubular corallines have no such protection, for which reason they are 

 not so often found in the turbulent parts of the ocean, as in sheltered re- 

 cesses of harbours, &c. 



The Pen-shaped Sertularia, or Sea Pen. — This coralline has a single pen- 

 nated stem ; the pinnse, or side small branches, are jointed and curvateJ ; 

 the denticles are ranged on one side, each supported by a little horn-like 

 tube ; they have a creuated margin, with a little spine on each side, oppo. 

 Bite to each other ; the ovaries are not knowai. This coralline is as remark- 

 able for the elegance of its form, as*its likeness to the feather of a pen. It 

 is of a yellowish brown colour, about five or six inches high. There are 

 many of them rise together from the same adhering tubes, with stiff jointed 

 stems. The little crooked tubes that support the denticles are longer iu 

 this species than in any of the like kind, being twice as long as the denticles. 

 It is not uncommon among the islands of the East Indies. 



The genus Sponge is exceedingly complicated, and still remains in much 

 doubt with various individuals. Colonel Montagu, in an essay on the na- 

 ture and constitution of sponges, in the Wernerian Transactions, is clearly 

 of opinion that they are animal substances, although no polypi, or vermes 

 of any kind, have as yet been discovered in their cells or pores ; and lie is 

 01 opinion that they possess vitality without perceptible action or motion, 



