2 BRITISH ZOOrilYTES. 



justified on the score of verbal accuracy, and is opposed both 

 to zoological and vulgar usages. In this work I use the 

 word in its restricted sense, as it was used by Ellis and 

 Solander, — or rather with a still narrower circumscription, 

 having assigned what appear to be sufficient reasons for re- 

 moving the Corallines and Sponges from the category. The 

 definition of a Zoophyte is thus considerably simplified, but 

 there still remains sufficient variety of structure in the con- 

 stituents of the order to render that definition vague, and, 

 perhaps, practically useless. Zoophytes are all aquatic, averte- 

 brate, inarticulate, soft, irritable, and contractile, without 

 a vascular or separate respiratory or nervous system. The 

 alimentary canal is very variable, but the aperture to it is 

 always superior, circular, edentulous, and surrounded by 

 tubular or, more commonly, by filiform tentacula. Many 

 are asexual, and it is doubtful whether any species has dis- 

 tinct sexes. — The individuals (Polypes) of a few families are 

 separate and perfect in themselves, but the great majority of 

 Zoophytes are compound animals, viz. each zoophyte consists 

 of an indefinite number of individuals or polypes organically 

 connected, and placed in calcareous, horny or membranous 

 cases or cells, forming, by their aggregation, corals or plant-like 

 Polypidoms. 



As thus defined, our Zoophytes are referable to two of the 

 primary divisions of the animal kingdom, — the Eadiated and 

 the Molluscan, — and consequently constitute two classes dis- 

 tinguished by a very remarkable dissimilarity of organization. 

 These classes have been named Anthozoa and Polyzoa, and 

 may be shortly characterized thus : 



I. — Anthozoa. Body tending to globular, contractile in every 

 part, symmetrical : mouth and vent one : gemmiparous 

 and oviparous. 



II. — PoLYzoA. Body elongate, syphonal, non-contractile, 

 and unsymmetrical : mouth and anus separate : oviparous. 



