22 



GENERAL ZOOLOGY 



beginning with the "Origin of Species" in 1859, rank as the 

 most notable contributions to biological literature of the nine- 

 teenth century, and perhaps of all time. The nature and extent 

 of the evidence upon which the theory of evolution rests will 

 be considered more in detail in later chapters. 



Taxonomy. — The science of classification is known as taxon- 

 omy. The theory of evolution teaches that all living things had 



Individual Cah 

 •SPECIES, domeshca 

 -GENUS, Fetis 

 .-FAMILY, Felidae 



-ORDER, Carn'ivora 

 ...CLASS, Mammalia 

 ... SUB -PHYL UM, Verlebrala 

 ..:PHYLUM, Chordaia 



...ANIMAL KINGDOM 

 .PLANT KINGDOM 



.-L/V/N6 WORLD 



p IG e_ — Diagram to show the tree-like form assumed by a natural system of 

 classification, as illustrated by the classification of the house cat, Felis domestica. 



an origin in some simple form or forms of protoplasm. From 

 these hypothetical ancestral organisms there first arose, pre- 

 sumably, the simpler forms of plant and animal life, and from 

 these in turn the higher forms. Thus it follows that a relationship 

 of varying degree exists between all forms of life — even animals 

 and plants being connected by simple unicellular forms, some 

 of which combine both animal and plant characteristics. 

 Lamarck was the first to express this relationship diagrammati- 

 cally by means of a tree whose trunk divides almost at once into 

 two main stems, one for the plant kingdom and one for the animal 



