6o AN INTRODUCTION TO ZOOLOGY. 



which are common to botli animal' and vegetable 

 organisms. Not only was the name new, but the 

 study; for such general problems did not come within 

 the scope of the zoology and botany of a previous day. 

 The earlier naturalists had supposed that the boun- 

 daries of the two great kingdoms of organic life, like 

 the boundaries of species, were arbitrary and fixed. 

 The forms that presented links between the two were 

 looked upon almost as monstrosities; nor were the 

 types usually adduced as links always those most 

 fitted to serve as such. The form was noted, rather 

 than the structure ; and the likeness between plants 

 and animals was illustrated by reference to animals 

 such as the sea-anemone, and other so-called Zoo^hyles, 

 which present no resemblance to vegetable forms 

 except in the radial symmetry which is the necessary 

 result of their fixed position (see Chnp. VI.), or in 

 the multipartite arrangement of their colonial forms. 

 But the resemblances brought to light by the investi- 

 gators of the present century are fundamental and 

 comprehensive ; indeed, so intimately connected are 

 the two great groups of living things that a know- 

 ledge of the one would be incomplete without some 

 reference to the other, as has already been shown in 

 the earlier chapters of this little volume. The " Dar- 

 winian theories," it will easily be understood, are not 

 less closely incorporated with the science of Biology 

 than with tlie science of Embryology. 



Since the introduction of the theories of Darwin, 

 the general ideas which are indicated by the terms 



