514 



TAXONOMY 



are closely related. Animals that carry their young in pouches are 

 classified together. Birds that have wading habits belong to the 



N. Y. Zoological Society 



The Armadillo (Tatu novencinctum) is covered with a bony shell. Some species can curl up 

 into a ball, presenting the armor on all sides. 



same group. Habits alone do not determine classification ; other 

 facts must be considered. The whale is frequently thought of as 

 a fish because it swims and lives in the water. Actually it is a 

 mammal because it suckles its young. When animals or plants 

 crossbreed with each other, they are usually found to be closely 

 related. For this reason successful crossbreeding is only possible 

 with those forms that are closely related. For example, the 

 horse and donkey will crossbreed and produce a mule. The mule 

 is probably always sterile, and will not produce offspring. Dogs 

 and wolves will crossbreed and the hybrid offspring will repro- 

 duce. Consequently, dogs and wolves are thought to be more 

 closely related than are horses and donkeys. 



The Law of Priority. So many modifications of Linnaeus' sys- 

 tem of classification arose that confusion resulted. An Interna- 

 tional Commission on Classification was founded in 1895. Its pur- 

 pose was to draw up a set of rules which would be accepted and 



