ON COLLECTING SHELLS. 289 



The great contractibility of pulnioniferous moUnsks at the 

 moment of death presents an obstacle to anatomical researches. 

 The real position of the organs becomes difficnlt to recognize, 

 and sometimes the delicate parts become injnred ; as the dart, 

 for example, broken and fixed in the liver or in other glands. 



On placing these mollusks in a vessel of water, closed and 

 deprived of "air, the exterior organs will be developed, as the 

 tentacles and the foot ; among others, the jaw becomes protruded ; 

 and npon adding a little tobacco the verge is plainly protruded 

 and may be recognized. Limaces confined dry in a morsel of 

 tobacco leaf die very quickly, their jaws and verges extruded. 



Clausilias ma}" be treated by covering the aperture of the shell 

 with wax, through which a hole may be pricked, large enough 

 to permit the passage of the animal, but too small to permit its 

 retraction after its tissues have become swollen b^' water; in this 

 way preparations can be made in which the jaws are thrust out 

 and the tentacles extended. — Morch. 



Naked mollusks may be mounted dry by preserving them in 

 a saturated solution of sal ammoniac and corrosive sublimate. 

 To prepare this solution, mix in water ten parts of the former 

 to one of the latter ; and since corrosive sublimate does not 

 easily dissolve in water, it may be previously mixed with alcohol. 

 Cuttle-fish, snails, etc., maj' be prepared with this mixture, which 

 will gradually harden them, whilst they retain both form and 

 color. The length of time that thej^ should remain in the 

 solution will var}^ according to the size of the object and the 

 density of its tissues. The only objection to this preparation 

 is its poisonous character. 



Naked mollusks may be preserved wet in a solution of one 

 part of alum to ten parts of water, in which they will retain 

 their colors better than in alcohol ; but no shells must be placed 

 in this solution, on account of its acid property. Sections of 

 spiral shells are prepared by applying the specimen to the side 

 surface of a grindstone ; they are useful to show the internal 

 characters ; and no better use of duplicates can be made than 

 to prepare at least one longitudinal and one transverse section to 

 illustrate each genus (i, 6, 8, 14 ; ii, 30 ; iv, 63). 



Shells are usually kept in drawers of convenient size for 

 handling, and about two inches in depth ; they are thus com- 

 pactly disposed and secluded from dust and light — the former 

 injuring their appearance, the latter causing the delicate colors 

 to fade. The few specimens too large to put in drawers may 

 constitute a display -cabinet for exhibition under glass in either 

 a horizontal or upright case. For eftectual preservation from 

 dust it is better to close in two rows of drawers with a pair of 

 doors ; which may have a lock for security. In the collection of 

 the. Academy of Natural Sciences of Philadelphia, the more 



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