72 HISTOllY OF BRITISH ZOOPHYTES. 



evident. Or had I, by way of experiment, changed the water, 

 it might to them have been fatal, for fresh-water might have 

 been death to the child of the briny waves, and sea-water 

 might have poisoned the offspring of the.fountains of water. 

 Since I wrote the above, my doubts have been removed by 

 my chancing to light on a passage in the valuable work of 

 the late Sir J. Graham Dalyell, who, by a long-continued 

 course of experiments and observations, was so remarkably 

 well acquainted with the nature and habits of our Scottish 

 polypes. He says, "Purity of the element in which zoo- 

 phytes dwell, seems more essential than sustenance. Slight 

 contamination is frequently fatal after the briefest interval. 

 Neither can fresh or salted water be substituted for each other 

 with impunity." From this we may conclude that the Vor- 

 ticella in the fresh and the salt water were different species, 

 though by the aid of a Codington lens I could not detect 

 the minute distinctions. 



The same author says, "Tentaculated zoophytes are ani- 

 mated products, simple or compound, resembling the form 

 and the efflorescence of plants. They constitute an immense 

 proportion of the organic world, that which has received the 

 smallest share of notice, and which is, perhaps, the least un- 

 derstood. It is only now that a ray of light begins to break 



