476 ELEMENTARY BIOLOGY 



The structure of organisms furnishes the basis for modern 

 classifications, but the word structure has a wide significance. 

 According to outward appearance we might place certain small 

 snakes with certain large worms ; but a study of the internal 

 structure at once separates them very widely. Again, the 

 appearance of certain caterpillars is much like that of certain 

 worms, but a study of the structure at various stages — that 

 is, the development — at once separates these two groups. 

 Modern classification of organisms accordingly considers all 

 that can be known about the living things, and not merely 

 their appearance or their uses. 



