72 



ESSAY ON SfONGES. 



currents or slight agitation in the water, whicfa 

 must have been perceived by the assistance of 

 glasses ^. Action, however, is by no means ne- 

 cessary to constitute an animal ; for in many in- 

 stances vitality is known to exist without mo- 

 bility. 



Zoophytes in general are destitute of loco-^ 

 motion ; and what action any of them possesses is 

 very limited, being chiefly confined to the multi- 

 farious polypi that constitute them. The only 

 genus of Zoophyta which is not possessed of polypes, 

 is Spongia ; and it is to be wished that this cha- 

 racter should be continued in contradistinction 

 to Alcyonium, which Mr Ellis established as the 

 basis of separation in the two genera. 



In the generic characters, Bosc has unfortunate- 

 ly omitted this essential distinction, as he has de- 

 scribed both genera to be polymorphous polypi^ 

 which should imply that spongia, as well as al- 

 cyonium, is constituted by polypes. This is con- 

 trary to all experience, and indeed is in direct op- 

 position to fact. 



It is not necessary that an animal body should 

 have motion to assure us of its animality, or that 

 it sustains vitality ; since life, in some of the lower 

 order of beings, is so infinitely diffused and vari- 

 ously modified ; at the same time that animal ac- 



* Mr Ellis speaks with certainty as to the contractive ani 

 expansive property of one species^ the cristata. 



