POLYPS. 67 
and is now commonly used. Minne Epwarps makes a separate 
class of these creatures, and places it amongst the Molluscs, after 
the naked Acephala, or Tunicata. Their arms are beset with cilia, 
which however are also remarked in some other Polyps, and conse- 
quently are not a distinctive character of Bryozoa, as would seem 
to be implied by the name Ciliobrachiata. To these Bryozoa belong 
the genera Alcyonella, Eschara, and Flustra. The remaining 
Polyps we shall name, with HHRENBERG, Anthozoa. 
The simple stomach of the Anthozoa is, for the most part, sepa- 
rated from the cavity of the body. In Actinia this space is divided 
into many prismatic cells by partitions that stretch perpendicularly 
- from the outer surface of the stomach to the innermost surface of 
the covering of the body. Similar partitions are found in many 
Anthozoa, though in much smaller number. One or more openings 
conduct from the bottom of the stomach to the cavity of the body, 
or to the general common cavity of the Polypstock!. In Hydra 
there is no special cavity of the body, but the cavity of the stomach 
is in immediate connexion with the walls of the body. It was 
formerly erroneously believed that the stomach of this animal is 
simply an excavation of its body, and that the structure of both 
surfaces is the same. The internal surface is coated with conical 
cells whose points are directed inwards?. The external surface, on 
the contrary, is formed of flat cells, and contains oval vesicles, from 
which a long delicate thread can be projected, (Angel-organ of the 
Germans”). TREMBLEY, amongst his many experiments on the 
reproductive power of the fresh-water Polyp, even turned the body 
inside out, like the reversed finger of a glove. Nevertheless, the 
creature continued to live, and took food. This may be explained 
by a change of structure, the consequence of the violence of the 
experiment. In Gryozoa, the intestinal canal is freely suspended in 
the cavity of the body: a longer or shorter cesophagus leads to a 
muscular stomach, lined, in some cases, with horny teeth, closely 
GRANT, as early as 1827, had observed the reverting intestinal canal, and the vibrating 
cilia on the arms of Flustra. Edinb. New Philos. Journ. ut. pp. 107—337. 
1 Lister, Philos. Transac. 1834, p. 371, Pl. vin. fig. 3 in Sertularia. Minne 
EDWARDS in the new illustrated edition of Cuvirr, Régne Anim. Zooph. Pl. uXxx. in 
Isis nobilis, &c. 
2 See Corpa, Nov. Act. Acad. Cesar. Leop. Carol. Natur. Curtosor. Tom. xv. 
Ann. des Sc. natur, Tome viit. Zoologie, p. 363. 
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