12 3i5otani2 



border-land where these two meet — and mingle. A 

 few decades ago we were told that the sponges 

 marked this indefinite land. Now, the sponges have 

 tlieir indubitable place in the animal kingdom, and 

 tlie microscope must direct our way to the wonder- 

 ful " What is it?" animal or vegetable? 



Cuvier found four characteristics which duly- 

 marked the animal from the plant : 1. A food 

 reservoir or stomach ; 2. Circulatory S3''stem ; 3. Lo- 

 comotion and sensibility, provided for by a more com- 

 plicated body containing nitrogen ; 4. Respiration. 

 In the years that have gone since Cuvier, we have 

 found that some animals lack the digestive appa- 

 ratus and some plants possess it. The test mark of 

 the circulatory system was practically given up by 

 Cuvier himself ; chemistry has annihilated the third 

 distinction, for nitrogen is as essential to plants as to 

 animals ; finally, the respiration of plants is as fully 

 marked as in many species of animals. 



What is the test-mark then, the broad arrow of 

 the animal kingdom ? Who knows ? Huxley tells 

 us that Professor Tyndall asked him to examine 

 some microscopic objects traveling in water " by 

 spasmodic wiggles." 



" What do you call them ?" asked Tyndall. 



" They may be animals, and then again they may 

 be vegetables," said liuxle}-. 



