12 3 APPENDIX. 



a few days in the solution of potash : and, finally, cleanse 

 it with some warm \\ater and a camel-hair brush. Spread 

 it out flat between slips of glass ; when dry, place it in 

 turpentine for a week, and afterwards mount it in 

 balsam. 



The best specimens for displaying the horny teetli with 

 which the gizzard is furnished are obtained from crickets, 

 grasshoppers, and cockroaches. 



PALATES (plate 6, figures 171, 172, 173, 174). These, 

 consist of a narrow kind of tongue, armed with a series of 

 horny teeth, placed in regular rows. The whelk, limpet^ 

 periwinkle, garden-snail, and the snails found in our cellais 

 and aquariums, are all furnished with this peculiar appara- 

 tus, which may be obtained by laying open the body with 

 the scalpel or scissors. It will generally be found curled up- 

 near the head, and may be distinguished by its ribbon-like 

 appearance : patience and skill are necessary to extract it 

 from the surrounding mass. When properly cleaned, it may 

 be at once pressed flat and dried between slips of glass. 

 Many palates polarize well when mounted in balsam ; but 

 if not intended for polarization, they shculd be mounted in 

 a preservative fluid, composed of five grains of salt to one 

 ounce of water. 



TONGUES, PROBOSCES, MANDIBLES, AND ANTENNAE 

 (plate 7, figures 197, 199, 202 to 204) are amongst the most 

 beautiful objects exhibited by the Microscope. Many of 

 these, besides the ligula, possess several sharp lancets for 

 puncturing the skin of animals from whom they derive their 

 sustenance. To arrange these organs so that each part 

 may be clearly seen, requires a good deal of delicate mani- 

 pulation. It is generally more satisfactory to mount the 

 whole head of the insect. To accomplish this, it must be 

 softened by immersion in liquor potassce for some time, and 

 the interior substance got rid of by pressure. To dry it 

 flat, place it between two slips of glass, which should be held 

 together by a spring-clip ; soak it for a fortnight or longer 

 in turpentine, until it becomes transparent, and then mount 

 it in balsam. 



The head of the bee, wasp, dronefly, blowfly, and gadfly, 

 are all excellent examples of the varied structures of these 

 suctorial organs. 



EYES (plate 7, figures 208, 208, 210). The compound 

 eyes of insects, for the display of their numerous facets, 

 should be dissected from the head, and macerated in fluid. 

 The black pigment lining the interior may be got rid of by 

 washing it away with a camel-hair brush. When quite 



