HISTORY OF ZOOPHYTOLOGY. 433 



are really animals ; — their quick and varied movements, — 

 their great irritability, — the existence of a mouth and sto- 

 mach, — the nature of their food, its digestion, and the evomi- 

 tion of the indigestible remains, are incontestible proofs of 

 this ; — and it seems improbable, to say no more, that this 

 animal should be fitted round with a case that grew independ- 

 ent of it and from a different cause. And the case itself has 

 no analogy, as Ellis shewed very clearly, either to bark or to 

 wood ; it possesses the structure of neither of them, nor is it 

 formed in the same manner by the addition of concentric 

 layers, nor does it contribute to the formation of new parts, 

 but, like the shell of testaceous mollusca, it is extravascular, 

 and when once formed suffers no other change than what 

 external injuries or time may operate. If possible, its coinci- 

 dences with the skin of cellular plants are even fewer : the 

 one is a living part, which has very important functions to per- 

 form in relation to the plant itself and to the atmosphere or 

 circumfluent medium in which it lives ; the other exhibits no 

 action characteristic of life, and is nothing more than a con- 

 densed albuminous or calcareous sheath, appropriated solely to 

 support or protection,* 



But, although I agree with the advocates of the animality 

 of zoophytes in general, I cannot go the length of Ellis in 

 considering it proved that sponges and corallines belong to the 

 same class. Ellis, we have seen, knew that no polypes were 

 to be found in sponge, and their existence in the pores of 

 corallines was inferred merely from the structure of these and 

 their chemical composition. They have been examined by 

 subsequent naturalists fully competent to the task, and under 

 the most favourable circumstances, — in particular by Cavolini 

 and Schweigger, — and the result has been a conviction that 

 these productions are truly apolypous. Now this fact, in my 

 opinion, determines the point, for if they are not the produc- 



* I do not enter into the question, whether the Confervas are real animals or not, 

 because, whatever conclusion we might adopt, they would not come within our defini- 

 tion of a zoophyte or polype, since they assuredly have neither mouth, tentacula, nor 

 stomach. Nor need I discuss the propriety of instituting, with Treviranus, a fourth 

 kingdom of animated nature, composed of the zoophytes and aquatic cryptogamia, as 

 my object and plan is only to describe what have been almost imiversally considered 

 zoophytes. 



F F 



