526 MOLLUSCOUS ANIMALS GENERALLY. 



These phenomena are of so novel and remarkable a character, that 

 they furnish an abundant source of interest to any Microscopist 

 who may happen to be spending the months of August and Sep- 

 tember in a locality in which the Purpura abounds ; since, by 

 opening a sufficient number of capsules, no difficulty need be 

 experienced in arriving at all the facts which have been noticed 

 in this brief summary.' It is much to be desired that such Mi- 

 croscopists as possess the requisite opportunity, would apply them- 

 selves to the study of the corresponding histoiyin other Pectini- 

 branchiate 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.^ 



353. Ciliary Motion on G-ills. — There is no object that is better 

 suited to exhibit the general phenomena of ciliary motion 

 (§ 276), 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 ot 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 animalcule cage, 

 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 aft'ord a general view 

 of this spectacle ; but a much greater amplification is needed, to 

 bring into view the peculiar mode in Avhich the stroke of each 

 cilium is made. Few spectacles are more striking to the unpre- 



' Fuller details on this subject will be found in the Author's account of his researches, 

 in the Second Series of the "Transactions of the Microscopical Society," vol. iii, p. 17; 

 and he would refer such of his readers as may be desirous of knowing what has been 

 done by other observers in regard to the development of ditferent species of Gastero- 

 pods, to the various Memoirs there cited. 



2 The Author thinks it worth his while to mention the method which he has found 

 most convenient for examining the contents of the capsules of Purpura ; as he believes 

 that it may be advantageously adopted in many other cases. This consists in cutting 

 off the two ends of the capsule (taking care not to cut far into its cavity), and in 

 then forcing a jet of water through it, by inserting the end of a fine-pointed syringe 

 (§ 132) into one of the orifices thus made, so as to drive the contents of the capsule be- 

 fore it through the other. These should be received into a shallow cell, and first exa- 

 mined under a single microscope. 



' This shell-fish may be obtained, not merely at the sea-side, but likewise at the shops 

 of the Fishmongers who supply the humbler classes, even in midland towns. 



