54 ZOOPHYTES. 



neously. Very few enjoy that faculty ; some only to the slightest extent. 

 All the Tuhularice and Sertularice are in this sense inflexible, in as far as I 

 am aware. Many zoophytes, indeed, including these genera in earlier, and 

 some in the latest stages, though growing upright, are incapable of sus- 

 taining themselves when deprived of their native element, which is not 

 rendered sufficiently explicit by those characterising them as flexible. 



But there are, in fact, several which are completely so. Single Vor- 

 ticellce, for example, can bend and turn and twist in all directions ; they 

 can almost cast a knot on their tender and delicate stems. Microscopic 

 shrubs composed of similar animals, hundreds of campanulate hydrse ter- 

 minating their extremities, while at their highest enjoyment of full ex- 

 pansion in some favourable position, will suddenly collapse on a momentary 

 alarm, crouching close down to the root in absolute quiescence. Then, as 

 if relieved from the apprehension of danger, they rise again to display 

 their beautiful proportions. — Plates XII. XXI. 



The younger and smaller Tubularise and Sertulariae consist of a single 

 hydra, sustained on a fistulous stem, a character unalterable with either 

 the age or dimensions of the indivisa. In some others it remains, while 

 flourishing twigs issue from the sides : but this is true only with respect to 

 the earlier specimens of many ; for in those which are older, such as the 

 Tubularia (Scrtularia) ramea, and the Sertularia ( Nemertesia) ramosa, the 

 stem having attained considerable diameter, will be found to consist of 

 numerous parallel tubuli ; and, in both it is quite inflexible, remaining up- 

 right, though the smaller parts yield when unsupported by the water. 



Different portions of the branches of the Tubularia ramea are indented 

 by whorls, and especially the extremities. — PI. VIII. fig. 3. But for the 

 most part they are faint or altogether obliterated : nor do these seem one 

 of the constant characters. 



The head or hydra of this product is deciduous, like the hydrse of the 

 two preceding species ; also like them, it enjoys the remarkable preroga- 

 tive of regeneration, — though perhaps for another purpose, because it is 

 not there that the elements of posterity reside as in the former. 



The duration of this most important part of its organization is inde- 

 finite. Of 80 vigorous hydrse which embellished the specimen, Plate VII., 



