142 Mr. W. Clark on the Animal of Kellia rubra. 



oblong, acuminated gradually, and sharply attenuated at the 

 apex, rounded or subtruncated, and somewhat inequilateral at 

 base, 3 inches long, 1| inch broad, upon a thick short petiole 

 of 2 lines in length. The flowers, sometimes in pairs, grow late- 

 rally at the base of the petiole ; the peduncle is refracted, j to 

 1 inch long, and covered with long glandular hairs mixed with 

 shorter stellate pubescence ; the calyx, also tomentose, is 8 lines 

 long, 6 lines across, inclosing a small globular berry 4 lines in 

 diameter. 



XVIII. — On the Animal of Kellia rubra. 

 By W. Clark, Esq. 



To the Editors of the Annals of Natural History. 



GENTLEMEN, Beacon Hill, Exmouth, Devon, July 5, 1849. 



I venture to trouble you with a few observations in reply to 

 Mr. Alder's last paper, in the f Annals ' of this month, on the 

 subject of Kellia rubra, and then I hope to retire from the field. 

 I have had ample scope allowed ; and though you have not in- 

 terrupted the discussion, by issuing the editorial veto, 



" Claudite jam rivos, pueri, sat prata biberunt," 

 still we ought to keep in mind the phrase, 

 " Est modus in rebus." 



Mr. Alder still continues to rely on the point that the regular 

 ingress and egress of the branchial currents, and the regulation 

 thereof, in the bivalve mollusca, are produced by the action of 

 the vibratile cilia, which clothe the branchial laminae; I differ 

 from his views, and think this doctrine entitled to no confidence, 

 and that the cause is inadequate to the effect propounded. 



The branchial cilia have very different functions ; their sole use 

 is to beat and subdivide the water, to facilitate the elimination 

 of the vital principle therefrom, after it has been admitted into the 

 branchial cavity by the opening of the valves of the animal, by 

 the relaxation of the adductor muscles, and from whence the im- 

 pure water is discharged by their contraction at the same points, 

 ventral or siphonal, or a combination of both, as the animal may 

 happen to be closed, or open mantled, at which it enters, and a 

 fresh supply of the pure element is received to fill the vacuum 

 caused by its expulsion. 



Great misapprehension has arisen from confounding the func- 

 tions of two different sets of organs, attributing to the one the 

 uses of the other, the real functions of which have altogether 

 been unnoticed. 



The assumed regularity of the admission and discharge of the 



U 



