30 ELEMENTARY ZOOLOGY. 



for the condition in the crystal which make it impossible 

 to break it into several complete crystals? Was this 

 true of the sand grain or the pebble. Does this strike 

 you as important? Why? Is this quality found in 

 shells, and plants, and animals? 



What qualities seem to you to distinguish the shells 

 from the crystals, pebbles, and sand? Are the different 

 regions of the shell more different from each other than 

 are the parts of the preceding objects? Justify your 

 answer. Find two or three terms that express this 

 idea. Which is the best term? Why? Do plants and 

 animals show this new quality which you have just named? 



In a similar way compare the plants and animals you 

 have observed with the forms that have gone before and 

 with one another, and note the points of similarity and of 

 contrast. 



40. Classification of objects on the basis of observed 

 qualities. 



a b c d e 



If you were asked to break up these six classes of objects 

 into two groups, which of the divisions indicated above 

 by the sets of brackets would you prefer? That is, 



