104 Hogg, on the Lingual Membrane of Mollusca. 



castor oil, Beale's creasote solution, Farrant's glycerine and 

 gum ; a few only are prepared dry. Of all the fluids em- 

 ployed balsam is certainly the worst ; it spoils or destroys all 

 the details of the more delicate tongues ; they are, indeed, 

 rendered so transparent that points of importance not only 

 escape observation, but errors of interpretation are very 

 likely to creep into our drawings and descriptions. By far 

 the most suitable medium for the greater number of tongues 

 is glycerine of various dilutions. The following method of 

 preparing and mounting I find successful: — After having 

 killed the mollusc by drowning in cold w^ater, with or with- 

 out a few drops of sweet spirits of nitre mixed in it, and 

 having removed as much of the soft parts as possible by re- 

 peated washings, or by cleanly dissecting out the tongue with 

 scaljDel and forceps, it may be put into a test tube containing 

 a small quantity of a weak solution of caustic potash. In a 

 few days it should be removed, Avashed with water, and sub- 

 sequently transferred to a very dilute solution of acetic or 

 hydrochloric acid. On removal from the acid it should be 

 washed with water, and immersed in a solution of glycerine 

 of the strength of one part Price's glycerine to two of distilled 

 water, and finally mounted in a shallow cell in the same 

 solution. Another medium found to answer well in some 

 instances is composed of three parts glycerine solution and 

 one part carbolic acid; the tongue in this instance must 

 be previously immersed in spirits of wine. Another medium 

 is comj)osed of two grains of bichloride of mercury, forty 

 grains of chloride of sodium, fourteen drachms of glycerine, 

 and eight ounces of water. This, if a cloud appear in the 

 solution, must be filtered through fine blotting paper. Some 

 of the tongues of marine species, Cephalopods in particular, 

 require much cleansing and washing before they can be 

 mounted ; then it is better to mount them dry in a dark cell. 

 The catalogue accompanying the prej)arations shows that 

 AVoodward approved of the tongue classification as projjosed 

 by Troschel, and he endeavoured to arrange his collection 

 accordingly. He, however, commences with CejDhalojDods, 

 four only of w^hich are found among the specimens, and 

 these by no means well or very suitably mounted. Ptero- 

 pods ; there is not a single specimen to represent this 

 family; Gasteropods forming nearly the whole of the col- 

 lection. The Pulmonifera are tolerably well represented. 

 The present possessor of the cabinet having added many 

 specimens, the total number is at the time of writing 

 about 240, inclusive, I believe, of a few sections of shells. 



