PLANTS AND ANIMALS DISTINGUISHED. 21 



CHAPTER II. 



PLANTS AND ANIMALS DISTINGUISHED. 



IT may seem an easy matter to draw a line between 

 plants and animals. Who cannot tell a Cow from a Cab- 

 bage? Who would confound a Coral with a Mushroom ? 

 Yet it is impossible to assign any absolute, distinctive 

 character which will divide the one mode of life from 

 the other. The difficulty of defining an animal increases 

 with our knowledge of its nature. Linnaeus defined it in. 

 three words ; a century later, Owen declared that a defi- 

 nition of plants which would exclude all animals, or of 

 animals which would not let in a single plant, was impos- 

 sible. Each different character used in drawing the boun- 

 dary will bisect the debatable ground in a different lati- 

 tude of the organic world. Between the higher animals 

 and higher plants the difference is apparent; but when 

 we reflect how many characters the two have in common, 

 and especially when we descend to the lower and minuter 

 forms, we discover that the two "kingdoms" touch, and 

 even dissolve into, each other. This border-land has been 

 as hotly contested among naturalists as many a disputed 

 frontier between adjacent nations. Its inhabitants have 

 been taken and retaken several times by botanists and 

 zoologists; for they have characters that lead on the one 

 side to plants, and on the other to animals. To solve the 

 difficulty, some eminent naturalists, as Hackel and Owen, 

 propose a fourth " kingdom," to receive those living be- 

 ings which are organic, but not distinctly vegetable or 

 animal. But a greater difficulty arises in attempting to 

 fix its precise limits. 



