268 ZOOPHYTES. 



(2.) Zoophytes exist as combined with inorganic matter, as the Ser- 

 tularia and the Flustra, growing, nevertheless, incorporated along with 

 themselves. 



A calcareous, cellular, or tubular secretion, seemingly derived from 

 the tenant, is seen in the Lepralia, Cellepora, and Tubipora. 



Farther, a substance partaking of animal nature, is combined with 

 the living inhabitant of the Alcyonium and the Lobularia : nor do these 

 differences now specified nearly exhaust the list. 



Perhaps we denominate many substances inorganic, from our igno- 

 rance of their true nature, just as substances are designed simple, which 

 chemists have failed in decomposing. 



The zoophyte is, therefore, purely animal, as in the first examples ; it 

 much resembles a plant in others, and in a third instance, the living crea- 

 ture inhabits a dwelling secreted from its own organization. 



The Hydra and the Actinia, both perfect animals, consist of a fleshy 

 sac, and in this, as in other things, the Hydra tuba or Strobila, resembles 

 them. They have a complete command over all their external organs, 

 and they are capable of shifting their site. The faculties of the Virgu- 

 laria and Pennatula are equivocal. 



Nearly all the others, in as far as I am aware, are rooted to the same 

 spot : they are denied the faculty of locomotion ; but some, as the Vorticella 

 and Pedicellina, can exercise a powerful influence over those portions which 

 we deem inorganic in others, as the Sertularia, Tubularia, and Flustra. 

 The latter can do no more than extend the tentacular organs, and slightly 

 alter the curvature and direction of the hydrse. The faculties of the Vor- 

 ticella and the Pedicellina, are greater. Certain species of the former can 

 almost cast a knot on the stem ; and the latter, by inflexion, can almost 

 touch the root with the summit. 



Zoophytes are naturally rigid or flexible : many require the aid of the 

 surrounding element in sustaining them upright : some are flexible in 

 early stages, and become rigid with age and increment. 



The like disparity appears in the size of zoophytes, as among other 

 classes of animals. The full-grown Sertularia pumila scarcely attains the 

 height of an inch : the Sertularia argentea, or Cupressina, reaches three 



