MICROSCOPIC OBJECTS. 35 



naturalist to determine the class of animals to which it 

 belongs. The magnifying powers required average from 

 100 to 300 diameters. 



Bone of Cuttlefish. — A thin vertical section of this sub- 

 stance offers an interesting subject for study, showing the 

 method adopted by the Creator for giving this animal the 

 greatest amount of sohdity with the least possible weight. 

 The carbonate of hme and animal matter of which this 

 substance is formed are deposited by the animal in plates, 

 separated by thin vertical columns, arranged in a zigzag 

 manner. To view the arrangement of the vertical co- 

 lumns to advantage, the object must be viewed by re- 

 flected light, and is prepared by taking off one of the 

 plates without disturbing the columns, which by a little 

 dexterity may be left attached to a lower plate. This 

 subject therefore furnishes two objects, the one being 

 prepared at right angles to the other. — Power 80 dia- 

 meters. By polarized light the piUars in the vertical 

 sections are distinctly seen ; and for this purpose it may 

 be mounted in Canada balsam. 



Bug. — The Cimex lectularius, or Bed Bug, is a popular 

 object for the microscope, and therefore must have a 

 place here. When mounted in Canada balsam it becomes 

 a permanent object, and when the specimen is perfect, 

 with the rostrum, or beak, laid out, and the lancets sepa- 

 rated, it becomes valuable. The spiracles, or breathing- 

 openings, along each side of the body, are worthy of 

 notice. The eggs have an operculum, or cover, and are 

 interesting opaque .objects. There are three other species 



E 2 



