38 MICROSCOPIC OBJECTS. 



and a description has been published, in which they are 

 considered as a cryptogamous vegetable. There is little 

 doubt, however, that they will prove to be the eggs of an 

 insect. They are often met with among old buildings, 

 attached to stones, in the crevices of slates, &c. 



The Elytra, or Wing-cases, of Insects are often singularly 

 engraved and coloured. Some (Curculiones) are covered 

 with beautiful iridescent scales, and others are furnished 

 with branched hairs. They are best seen by strong re- 

 flected light. A punctated form of el}i:ron is seen in 

 the Elaphrus beetles. The wing- covers of the Cercopis 

 sanguinolenta are interesting transparent objects, mounted 

 in balsam. The large elytra form good objects for the 

 screen of the oxyhydrogen and solar microscopes. 



The elytron of the Diamond Beetle is best viewed by 

 the microscope when mounted in a cell filled with Canada 

 balsam, and covered with a plate of glass. This method 

 not only protects the scales upon the wing from dust and 

 injury, but by rendering the refractions of the surface 

 more uniform improves the vision. 



Entozoa. — There are no less than fourteen distinct 

 species of these creatures found in the human body. 

 They are mostly inclosed in a long oval cyst, which is 

 sometimes imbedded in the muscles. To unassisted 

 vision the cysts appear as white specks about -^q^ of an 

 inch in length. 



Exuvice. — Insects, spiders and many of the Entomo- 

 stracea, shed their skins several times during growth. 

 These exuviae, or cast skins, being very transparent, afPord 



