Mollubks. 4597 



writing, specimens without any colour on either side; specimens coloured on both 

 sides; and specimens with both eyes and the whole of the colour on the left side in- 

 stead of the right. Those without any dark colour on either side are albino varieties, 

 through the transparent skins of which the colour of the blood-vessels and muscles 

 has suggested the trivial names of rosea and carnaria to the authors who considered 

 them species." Through the kindness of Mr. Jenner Weir I have before me a speci- 

 men of the flounder which seems to present some peculiarities : both sides are white, 

 but the eyes themselves are of the usual colour, and without that peculiar red tinge 

 which usually characterises albinos: there is no rosy or flesh-coloured tint on either 

 side, and the blood-vessels and muscles are not discernible through the cuticle, so that 

 this appears to be quite distinct from that peculiar freak of nature called albino. — 

 Edward Newman. 



Shell-fish burroiving into Rocks, ^-c.-Mr. Charlesworth * gave an account of the 

 various theories which have been advanced by naturalists, to explain the remarkable 

 power possessed by certain kinds of shell-fish, of burrowing into rocks, hard timber, 

 and other substances. The hypothesis explanatory of this curious phenomenon, to 

 which he first adverted, was that of Mr. Garner, an hypothesis which deserves especial 

 consideration, from it being adopted by so high an authority as Professor Owen. Mr. 

 Garner supposes that the currents of water produced by the movements of the vibratile 

 cilia, or hair-like processes with which some portions of the bodies of shell-fish are 

 covered, is the chief agent by which the burrows of these creatures are hollowed out. 

 Mr. Charlesworth considers this theory untenable on two grounds: one, the extreme 

 improbability that currents of so feeble a character as those produced by the cilia of 

 shell-fish could sink holes in rocks of the hardest limestone, even if the excavation of 

 these holes occupied a period of a thousand years, instead of being, as is well known, 

 effected in a few days or weeks ; the other, that of there being a limit to the depth of 

 the burrows, for all stone-boring shell-fish leave off excavating when they have lodged 

 themselves at such a distance from the surface of the stone as is consistent with their 

 own security and the supply of their wants. Now the ciliary currents alluded to by 

 Mr. Garner are in motion during the whole life-time of these creatures. If, then, 

 these currents scoop out the holes in question, a burrowing shell-fish through life would 

 never cease to deepen its excavation, a condition which is not found to be borne out 

 by fact. A more generally received hypothesis, and one of much earlier origin than 

 the above is, that shell-fish bore into stone by a rotation of their own shell, which is 

 assumed to act as an auger or drill, and to be sufficiently hard to file away those por- 

 tions of solid bodies against which the instinct of the contained animal directs it. 

 The characters of the Pholas, a shell whose burrows may be seen at low tide on the 

 scar at Whitby in the greatest profusion, favour this theory, since its shape is cylin- 

 drical, and its surface studded with numerous short strong spines, apparently well 

 adapted for rasping. Mr. Charlesworth, however, could not accept the mechanical 



* At the Meeting of a Natural-History Club at York. 

 XIII. 



