Mr. J. Alder on the Animal of Kellia rubra. 383 
very efficient aid by exciting discussion. On these natural phe- 
nomena we cannot at once apply mathematical demonstration, 
but must be content to obtain facts, and arrive at truth by im- 
ductions, in the first instance, from hypothesis. 
I am, Gentlemen, your most obedient servant, 
WiriiaM Criark. 
P.S.—Since the above observations were written I have ex- 
amined a great number of the Lagena striata, and have no doubt 
that, like the Layena levis, they form in their natural habitat, a 
fixed stem of cells piled on each other. 
XLI.—On the Animal of Kellia rubra. 
By Josuua AtpEr, Esq. 
To Richard Taylor, Esq. 
DEaR SiR, Newcastle-on-Tyne, April 18, 1849. 
Can you spare me room in the next Number of the ‘ Annals’ 
for a few remarks on Mr. Clark’s interesting letter on Kellia 
_ rubra? 
I am glad to find that Mr. Clark is enabled to confirm my 
statement that the anterior tube of this species is an open fold of 
the mantle : the only difference now between us is as to its uses, 
involving the question of the mode of supplying a current of water 
for respiratory and alimentary purposes. 
In cases where a matter of fact is in dispute, it is always best, 
before arguing the point, to test the truth of former observations. 
On reading Mr. Clark’s letter, therefore, I resolved, as he had 
done, to submit this little bivalve to a re-examination ; and ac- 
cordingly applied to my friend Mr. Cocks of Falmouth to send 
me a few specimens by post, as it is rather difficult to procure on 
our part of the coast. Mr. Cocks very obligingly and promptly 
complied with my request by sending me above a hundred spe- 
cimens, which, after a land journey of nearly 500 miles, arrived 
quite fresh, and immediately showed signs of life on being put 
ito sea-water. I placed two or three of these in a watch-glass 
under the microscope, and examined them by transmitted lght, 
the mode I had before employed with success to observe the cur- 
rents in this species as well as in K. suborbicularis. By this 
means I distinctly saw, as on former occasions, a continuous cur- 
rent of water flowing into the anterior tube; indicated by the 
minute floating particles it contained, which were gradually drawn 
towards the tube, and one after another passed into it im quick 
succession. In this manner I examined many individuals, and 
always with the same results. When the water is perfectly clear 
