348 ANNUAL OF SCIENTIFIC DISCOVERY. 



stream, and soon begins to crumble in pieces by the action of the 

 water and collision of the sand, till at length each minute individual 

 becomes free and is left to take charge of itself. It then begins to 

 exert volitions for its own safety and provision. Many, if not all, of 

 the species, in this condition, spin from their bodies, near the foot, a 

 filament resembling silk, by which they attach themselves to adjacent 

 objects which are fixed and solid, such as shells, sticks and stones. I 

 have frequently seen them anchored to their mothers. This filament 

 is deciduous, and disappears as they advance in age and size. 



ON THE BORING POWER OF THE PHOLAS DACTTLUS. 



MR. JOHN ROBERTSON, Brighton, England, communicates to the Edin- 

 burgh Journal the following observations on the boring power of the 

 Pholas dactylus : "I have endeavored during the last six months to 

 discover how this mollusc makes its hole or crypt in the chalk : by a 

 chemical solvent ? by absorption ? by ciliary currents ? or by rotatory 

 motions 1 My observations, dissections, and experiments set at rest 

 all controversy in my own mind. Between twenty and thirty of these 

 creatures have been at work in lumps of chalk, in sea-water in a glass 

 and a pan, at my window, for the last three months. 



The Pholas dactylus makes its hole by grating the chalk with its 

 rasp-like valves, licking it up, when pulverized, with its foot, forcing 

 it up through its principal or branchial siphon, and squirting it out in 

 oblong nodules. The crypt protects the Pholas from conferva, which, 

 when they get at it, grow not merely outside, but even within the lips 

 of the valves, preventing the action of the siphons. In the foot, there 

 is a gelatinous spring or style, which, even when taken out, has great 

 elasticity, and which seems the main-spring of the motions of the 

 Pholas dactylus. 



ON THE ECONOMICAL USES OF THE SKIN OF THE WHITE PORPOISE. 



MR. T. S. HUNT, of the Canadian Survey, presented a communication 

 to the American Association, Albany, on the " Economical Value of 

 the Skin and Oil of the White Porpoise," the uses of which have re- 

 cently been brought before the public by M. Tetu, of Canada. 



This cetacean, the Delphinus leucas, is a native of the Arctic Seas, 

 particularly of the Gulf of St. Lawrence and Hudson's Bay, where it 

 attains a length of from twelve to twenty feet. Its color is of a nearly 

 uniform creamy white. The fisheries of these animals, already some- 

 what extensive, are principally in the lower St. Lawrence. The oil 

 extracted from them is extremely valuable, furnishing purer oleine 

 than that obtained from any other natural source. In good seasons, a 

 porpoise of twenty feet yields 150 gallons. This oil is now employed 

 exclusively for the light-houses of the lower St. Lawrence, the Board 

 of Commissioners having, after a careful trial, given it a preference over 

 all other oils for illuminating purposes. The skin of this porpoise, 

 freed from its epidermis, and a thick mucous layer which underlies it, 

 has been found to be capable of being made into leather of a very 

 superior quality. This process is, in many respects, very different from 



