PLANTS AND ANIMALS 219 



siderations, and having in mind the simplest 

 organism, it is evident as soon as mentioned, 

 that the first structure likely to be present, 

 aside from the indispensable cytoplasm and y, 

 nucleus, would be a cell wall. The cell wall is versa! structure 

 the shield, the armor, the enveloping cloak, 

 that the organism throws about itself to pro- 

 tect the living, delicate protoplasm from the 

 rough contact and harmful influence of the 

 outer world. Some protection is well nigh 

 indispensable upon the free surfaces. For the 

 unicellular organisms it is a cell wall ; for the 

 multicellular organisms the walls about the 

 cells of part or all of the tissues persist, or else 

 only the general free surfaces develop walls. 

 It is in the nature of this almost universal in- 

 vestment that it is proposed to point out a. 

 fundamental distinction between animals and 

 plants. 



In attempting to distinguish animals and 

 plants by means of definite characters, there 

 is, however, another point that first needs 

 attention. Diagnostic characters can onl3^be 

 drawn between like things, and in so far as 

 the characters are also fundamental they 

 must be based upon fundamental features. In 

 searching for essential points of resemblance 

 or dissimilarity, it cannot be denied that the 

 normal individual in possession of its full 



