MICROSCOPIC OBJECTS. 45 



but not of uniform texture ; hence its examination under 

 the microscope possesses interest. — Mean diameter -g-^o^^ 

 of an inch. — Magnifying power 175 diameters. 



Heads, Insects. — The manducatory apparatus of insects 

 is a subject of great interest to the entomologist. The 

 two grand divisions of insects into Mandibulata and 

 Haustellata are founded thereon ; the former division 

 having jaws, the latter a proboscis or sucking- instrument. 

 As microscopic subjects, when admissible, it is well to have 

 them presei'ved in situ, as also dissected. The heads of 

 beetles, butterflies, and moths, form excellent opaque 

 objects, and instruct us as to the arrangement and dis- 

 position of the eyes, mouth, palpi, antennae, &c. 



Horse Hoof, section of — resembles in structure that of 

 whalebone. By polarised light, and a thin plate of sele- 

 nite being placed under the object, it is very beautiful. 

 -r-Magnifying power 100 diameters. 



Infusoria. — In the Catalogue only those genera are 

 given which can be preserved dead. By far the greater 

 number are loricated — that is, covered with a shell ; this 

 shell in some genera is composed of silica; in others car- 

 bonate of lime forms the basis. These shells may be 

 mounted in Canada balsam. The softbodied animalcules, 

 when mounted, by drying on a sHp of glass serve prin- 

 cipally to illustrate their muscular system, or when pre- 

 viously fed on coloured substances, as indigo, carmine, 

 sap green, &c., to show the form of their digestive 

 organs. In general, however, when dried, they lose 

 much of their external characters, and possess, except 



