476 ELEMENTARY BIOLOGY 



The structure of organisms furnishes the basis for modern 

 classifications, but the word stmcture 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. 



