CHAPTER II. 



THE CLASSIFICATION OF ANIMALS. 



(Taxonomy.) 



HEN we come to regard this earth as a whole, with 

 everything upon it, it can be stated that it is made up 

 of two kinds of matter. By far the lesser portion of 

 this material is living matter, while the balance is not 

 living matter, and for the distinct gap separating these tw r o, the 

 biologist knows of no link. Whatever life may be, when it ceases 

 in the protozoan, in the animal, or in the plant, what remains is 

 at once claimed by the world of lifeless matter, and is thereafter 

 subject only to the chemical changes of either disintegration or 

 of decomposition. Later on it may be taken up again into living 

 material. 



Now, the consideration of all living matter, with the phenom- 

 ena it manifests, falls to the science or sciences of biology, while 

 the dealing with dead matter belongs to another distinct cate- 

 gory known as the abiological sciences. The science of zoology 

 is an example of the first, and geology of the last. Again, we 

 have animal-life and plant-life; organic forms and non-organic 

 forms; and so, once more considered in its entirety, structures of 

 all kinds exhibiting the phenomena of life are divisible into two 

 great kingdoms the animal and the vegetable. As we pass to 

 the forms of the greatest simpleness in either of these, no zoolo- 

 gist or botanist can with a steady hand draw the hard and fast 

 dividing line between them. 



Still, this has been attempted, and Dyer has truthfully said that 

 the " fundamental difference which separates the vegetable king- 

 dom from the animal kingdom is to be found in the modes of nu- 

 trition which obtain in each. If we compare a plant and animal 

 reduced to their simplest terms, and consisting, therefore, in 

 cadi case of a single cell, i. e., of a minute mass of protoplasm in- 

 vested with a cell-well, while the unicellular plant draws its nu- 

 triment by simple imbibition through the cell-wall from the sur- 

 rounding medium a process which implies that all its nutriment 

 passes into it in a liquid form the unicellular animal is able to 

 take in solid nutriment by means of interruptions in the con- 

 tinuity of the cell-wall, and is also able afterward to reduce this 



