332 MANIPULATION. 



near the outer margin of the valves of the shell ; these, after 

 having been washed and dried, may be mounted In Canada 

 balsam in the usual manner. Some shells of the genus 

 Pinna, that exhibit a prismatic structure, wiU separate readily 

 into prisms ; these may also be mounted either in fluid or in 

 balsam without any further preparation. The most difficult 

 shells to cut are those whose structure is nacreous or pearly — 

 the ear shell, Haliotis, is the best example of this kind ; these, 

 however, will yield to the file and hone; sections of them 

 should be decalcified, and it wiU then be seen (as was dis- 

 covered by Dr. Carpenter) that the splendid hues which this 

 tribe of shells presents are due to the plication of the animal 

 membrane. Amongst the shelly tissues may be mentioned 

 the spines of the Echinodermata, the tegument of the Crus- 

 tacea, and the bone of the Cuttle fish. AU these may be 

 prepared in the same manner as shells, by the file and -the 

 hone, with the exception of the last, which may be cut suf- 

 ficiently thin with a very sharp knife. The spines of the 

 Echini, after having been cut transversely with a saw, and 

 then ground down and mounted in Canada balsam, form some 

 of the most beautifid objects for a microscope of low power ; 

 considerable difficulty will, however, be found in getting a 

 section perfect and at the same time very thin. A portion of 

 the shell of a crab, taken from one of the large claws, also 

 forms a most interesting object ; but the author would refer 

 those who wish to obtain a knowledge of these beautiful 

 structures to the very valuable papers of Dr. Carpenter in the 

 Reports of the British Association for the Advancement of 

 Science, where he wiU also find accurate representations of 

 the most remarkable kinds. 



To make Sections of hard Vegetable Tissues. — The dense 

 structures which compose the stones of some of the pulpy 

 fruits, such as the peach, apricot, plum, and cherry, are 

 beautiful objects for microscopic investigation ; they resemble 

 in a very striking manner the osseous tissues of animals, and 

 like them require to be cut into thin slices in order to exhibit 

 their true characters. The principal instruments necessary for 

 this purpose will be the saw, the file, and the hone; those 



