618 CILIARY MOTION ON GILLS OF MOLLUSKS. 



brief summary. * It is much to be desired that such Microscopists 

 as possess the requisite opportunity, would apply themselves to 

 the study of the corresponding history in other Pectin ibranchiate 

 Gasteropods, with a view of determining how far the plan now 

 described prevails through the Order. And now that these 

 Mollusks have been brought not only to live, but to breed, in 

 artificial Vivaria, it may be anticipated that a great addition to 

 our knowledge of this part of their life-history will ere long be 

 made. 



481. Ciliary Motion on Gills. — There is no object that is better 

 suited to exhibit the general phenomena of Ciliary Motion (§ 352), 

 than a portion of the Gill of some Bivalve Mollusk. The Oyster 

 will answer the purpose sufficiently well ; but the Cilia are much 

 larger on the gills of the Mussel, + as they are also on those of the 

 Anodon or common Fresh-water Mussel of our ponds and streams. 

 Nothing more is necessary than to detach a small portion of one 

 of the riband-like bands, which will be seen running parallel with 

 the edge of each of the valves when the shell is opened ; and to 

 place this, with a little of the liquor contained within the shell, 

 upon a slip of glass, — taking care to spread it out sufficiently with 

 needles to separate the bars of which it is composed, since it is on 

 the edges of these, and round their knobbed extremities, that the 

 Ciliary movement presents itself, — and then covering it with a 

 thin -glass disk. Or it will be convenient to place the object in the 

 Aquatic Box, which will enable the observer to subject it to any 

 degree of pressure that he may find convenient. A magnifying 

 power of about 120 diameters is amply sufficient to afford a 

 general view of this spectacle ; but a much greater amplification 

 is needed to bring into view the peculiar mode in which the stroke 

 of each Cilium is made. Few spectacles are more striking to the 

 unprepared mind, than the exhibition of such wonderful activity 

 as will then become apparent, in a body which to all ordinary ob- 

 servation is so inert. This activity serves a double, purpose ; for 

 it not only drives a continual current of water over the surface of 

 the Gills themselves, so as to affect the aeration of the blood, but 

 it also directs a portion of this current (as in the Tunicata, § 453) 



* Fuller details on this subject will be found in the Author's account 

 of his researches, in "Transactions of the Microscopical Society," 2nd 

 Ser., Vol. iii. (1855), p. 17. His account of the process has been called in 

 question by MM. Koren and Danielssen, who had previously given an 

 entirely different version of it, but has been fully confirmed by the ob- 

 servations of Dr. Dyster; see "Ann. of Nat. Hist.," 2nd Ser., Vol. xx. 

 (1857), p. 16. The independent observations of M. Claparede on the 

 development of Neritina jiuviatilis (" Midler's Archiv.," 1857, p. 109, and 

 abstract in "Ann. of Nat. Hist.," 2nd Ser., Vol. xx., 1857, p. 196) show 

 the mode of development in that species to be the same in all essential 

 particulars as that of Purpura. 



t This Shell-fish may be obtained, not merely at the Sea-side, but like- 

 wise at the shops of the Fishmongers who supply the humbler classes, 

 even in Midland towns. 



