CORRIGENDA ET ADDENDA. 613 



of the insect are allowed to dry, air gets into them, and it 

 is almost impossible to get it out again; by this plan, they 

 need never get dry. Some practice and manipulative dex- 

 terity are, of course, necessary to mount these objects well. 

 Strong acetic acid will clean insects, but not so quickly as 

 the potass. This has the same disadvantage as the liquor 

 potassae in containing water : a medium is required which 

 will destroy the muscular tissues, soften the chitine, and 

 combine with turpentine or balsam ; this medium, I be- 

 lieve, the Rev. J. Thornton, of Asten Abbots, has found 

 out, and by this means he is enabled to mount the very 

 beautiful insects which we see about. 



" The addition of sulphuric acid to the nitric acid, in 

 destroying the animal matter of guano, I have also found 

 to be useful. 



" In covering objects, I have found that by wetting the 

 cover with turpentine before dropping it on the balsam, 

 it prevents the accumulation of air-bubbles." 



P. 415.] Mr. Harper, having closely observed the boring 

 PholadeSj says: 



"They work with a < hyaline stylet/ and, as far as I have 

 been able to learn, there is very little indeed said about 

 the organ in question, even in professedly scientific books. 

 Its use up to the present time has been a mystery, but 

 the general opinion of authors seems to be, that it is the 

 gizzard of the Pholas. This I very much doubt, for it is 

 my belief that the presence of such an important muscle 

 is solely for the purpose of aiding the animal's boring 

 operations. Being situated in the centre of the foot, we 

 can readily conceive the great increase of strength thus 

 conveyed to the latter member, which is made to act as 

 a powerful fulcrum, by the exercise of which the animal 

 rotates, and at the same time presses its shell against and 

 rasps the surface of the rock. The question being asked, 

 ' How can the stylet be procured to satisfy curiosity 1 ' I 

 answer, by adopting the following extremely simple plan : 

 Having disentombed a specimen, with the point of a sharp 

 instrument cut a slit in the base of its foot, and the object 

 of your search will be distinctly visible in the shape of, if 

 I may so term it, an opal cylinder. Sometimes I have 



