12 - HISTORY 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- 
ficelle 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 
