COMPENDIUM. 271 



by a short stem half an inch across, diverging sparingly into boughs and 

 branches, with about an hundred extremities, bearing thousands of hydra:, 

 a tuft of an inch in diameter separated. The Sertularia now described 

 consisted of a number of slender parts. A tuft separates also on rending 

 the Tubiilaria ramea from its site. But all the descending part of the 

 Tulmlaria indivisa appears to be a simple prolongation of the stem. 



The original cell of the foliaceous zoophytes is horizontal ; none 

 other rise immediately above, and the animated leaf rises vertically from 

 one side of it, leaving it thus to constitute the root. All the rest of the 

 cells indent the vertical leaf of later origin, a natural device of the most 

 wonderful description. The dimensions of the foundation-cell, however, 

 are alike restricted as those of the root of most Sertularia?. 



All the provisions of Nature whereon human judgment may be exer- 

 cised, seem so admirably adapted to the original condition of her products 

 undisturbed, that the rivetting power of the root will be probably found 

 proportioned to the rigidity or flexibility of the stem, and the violence 

 necessary to resist divulsion. 



Some may be sheltered from violence by their native site, that is the 

 place best adapted for salubrity. 



Should this be true, that product most imperfectly rooted should be 

 the least exposed. 



But zoophytes may attain considerable size without either sensible 

 root or radicles. The Alcycmium gelatinoswm has none. A beautiful fleshy- 

 like specimen, above ten inches high, grew on a small shell of the Venus 

 Islandica — one not fifteen lines in diameter. On disruption it separated 

 quite clean and smooth, with a slight depression in the under surface of 

 the adhering base, which itself was under two lines across. 



The adhesion of the Lobularia is of a different kind, resembling that 

 of the Ascidia. It is firm, but there are no radicles. On the contrary, 

 a skin seems interposed to cover the integument of the base of the Lobu- 

 laria, as it spreads and enlarges by successive generations ; and it is so in- 

 timately applied to the substance invested, that divulsion uninjured is 

 seldom practicable. 



A few zoophytes, void of all fixture, are free. The Cristatella may 



