COLLECTING SALT-WATER SPECIMENS. 267 



using an acid solvent in the following manner. If a sufficient quantity 

 of hydrochloric acid, considerably diluted with water (say one part acid 

 to twenty-four of water), be poured upon a shell contained in a glass 

 vessel, it will soon exhibit a soft floating substance, consisting of 

 innumerable membranes, which retain the figure of the shell, and 

 afford a beautiful and popular object for the microscope. In analysing 

 shells of a finer texture than such as are generally submitted to the 

 test of experiment, the greatest circumspection is necessary. So much 

 so, that M. Herissant, whose attention was particularly devoted to the 

 subject, after placing a porcelain shell in spirits of wine, added, from 

 day to day, for the space of two months, a single drop of spirits of nitre, 

 lest the air, generated or let loose, by the action of the hydrochloric 

 acid on the earthy substance, should tear the net-work of the fine 

 membranaceous structure. This gradual operation was attended with 

 complete success, and a delicate and beautifully reticulated film, re- 

 sembling a spider's web in texture, rewarded the patience of the 

 operator the organisation of which film, from its extreme fineness, he 

 was not, however, able to delineate. In shells of peculiar delicacy, 

 even five or six months are sometimes necessary for their complete 

 development ; but in others of a coarser texture, the process is soon 

 completed. 



ON COLLECTING SALT-WATER SPECIMENS. 



" Nothing," as Dr. Harvey says, "can exceed the beauty of a clear 

 rock-pool, seen under strong sunlight, and through a calm surface, 

 tenanted by its various animated tribes all fulfilling the duties allotted 

 to their several kinds. Careful examination with a lens will generally 

 detect a multitude of minute shells, some of very strange shapes, and 

 others possessing structures of great elegance. These are the various 

 species of Foraminifera. We should recommend these species to be 

 studied in a living condition, whenever opportunity presents, as it 

 will prove a study of great interest. The drift-sand will often be 

 found to contain a wonderful variety of minute spiral univalve shells, 

 though these are scarcely of so small a size as to come Avithin the list of 

 microscopic objects. Others may be obtained by the gatherers of sea- 

 weeds, with little trouble, if they will only preserve the sediment that 

 collects in the water in which the sea-weeds are washed. When the 

 sea-weeds are plunged into fresh water, these minute molluscs (Eissoce) 

 are quickly killed, and fall to the bottom, and may then be secured 

 by simply straining the water through a piece of canvas. Many other 



