Mr. J. Alder on the Animal of Kellia rubra. 383 



very efficient aid by exciting discussion. On these natural \)\\?e- 

 nomena we cannot at once apply mathematical demonstration, 

 but must be content to obtain facts, and arrive at truth by in- 

 ductions, in the first instance, from hypothesis. 



I am, Gentlemen, your most obedient servant, 



William Clark. 



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 Lagena Icevis, they form in their natural habitat, a 

 fixed stem of cells piled on each other. 



XLI. — On the Animal of Kellia rubra. 

 By Joshua Alder, 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 j\Ir. Clark^s interesting letter on Kellia 

 rubra ? 



I am glad to find that JNIr. 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 IMr. 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 mimediately showed signs of life on being put 

 into sea-water. I placed two or three of these in a watch-glass 

 under the microscope, and examined them by transmitted light, 

 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 in quick 

 succession. In this manner I examined many individuals, and 

 always with the same results. When the water is perfectly clear 



