INTRODUCTION 



IT is customary to place all living beings in either the animal or 

 vegetable kingdoms, but in reality a sharp boundary line between 

 animals and plants first becomes possible when they exhibit a 

 complicated structure. In those of more simple organisation all 

 distinctions disappear, and it becomes difficult to define the exact 

 limits of Botany and Zoology. This, in fact, could scarcely be 

 otherwise, as all the processes of life, in both the animal and vegetable 

 kingdoms, are dependent on the same substance, protoplasm. With 

 more complicated organisation, the specific differences increase, and 

 the characteristics distinguishing animal from vegetable life become 

 more obvious. For the present, it must be confessed, the recognition 

 of an organism, as an animal or a plant, is dependent upon its corre- 

 spondence with an abstract idea of what a plant or animal should 

 be, based on certain points of agreement between the members of 

 each class. A satisfactory basis for the separation of all living 

 organisms into the categories of animals or plants can only be 

 obtained when it is shown that all organisms distinguished as 

 animals are in reality genetically connected, and that a similar 

 connection exists between all plants. The proof of this can only be 

 arrived at through the THEORY OF EVOLUTION. 



From the study of the fossil remains and impressions of animals 

 and plants, it has been established that in former epochs forms of 

 life differing from those of the present age existed on the earth. 

 It is also generally assumed that all living animals and plants have 

 been derived by gradual modification from previously existing forms. 

 This leads to the further conclusion that those organisms possess- 

 ing closely similar structure, which are united as species in a 

 genus, are in reality related to one another. It is also probable 

 that the union of corresponding genera into one family and of families 

 into higher groups serves to give expression to a real relationship 

 existing between them. 



The presumable origin of a living organism from others previously 

 existing has been distinguished by HAECKEL ( x ) as its phylogenetic 



