8 SYSTEMATIC ZOOLOGY. 



communicating the sensation of sight, one for 

 sound, one for tafcte, and one for smell. Some of 

 the other divisions of animals have more or less 

 of these organs in greater or less perfection. 



All animals seem to require a system of organs 

 for digesting food, for circulating fluids through 

 the body, and for oxy dating those fluids. In ver- 

 tebral animals these organs consist of stomachs, 

 to which an alimentary canal is attached ; a heart 

 which is alternately compressed and expanded; 

 to which a set of arteries and veins are attached 

 the former for conveying the fluids from the heart, 

 and the latter for returning them to the heart ; lungs 

 or gills in which the same fluids are presented to the 

 oxygen of the atmosphere. Some animals have 

 their fluids oxydated by means of spiracles, some 

 by means of exterior membranous organs. 



SYSTEMATIC ZOOLOGY. 



Animals are distributed into groups, for the 

 convenience of ascertaining their names and of 

 studying their affinities. These groupes or as- 

 semblages are called Classes, Orders, Genera ; 

 Species and Varieties, 



LINNEUS distributed all animals into six classes, 



1. Mammalia, viviparous and suckling the young, 



2. Jives, oviparous, having two wings and two 

 feet. 8. Amphibia, lungs adapted to long sus- 

 pended respiration. 4. Pisces., fins and gills sub-* 

 stituted for lungs. 5. Insecta, antennae in most 

 cases, members articulated to an external crust. 

 6. Vermes, body soft, members not articulated, or 

 wanting. 



CUVIER subdivided several of these classes. 

 Mammalia, Jives, Jlmphibia and Pisces remain a& 



