228 



NATURE STUDY. 



blances, rather than differences, and to recognize simi- 

 larity of plan or cause or law, we must endeavor to 

 first associate or bring together and compare those 

 objects which resemble one another, and then those 

 which differ more. The results will be much better if 

 we compare the crayfish with the lobster (see Fig. 26), 

 and then with the crab to get the idea of Crustacea, 

 than if we first compare crayfish and crab, which are so 

 different from each other. 



Fig. 26. Lobster. 



After resemblances are seen they can be emphasized 

 by contrasting animals which are similar with those 

 which are dissimilar. After the children have discov- 

 ered that crayfish and crab and lobster are alike in hav- 

 ing two divisions of the body and five pairs of legs, 

 they can be compared with the grasshopper (Fig. 27), 

 which has three divisions of its body and three pairs of 

 legs. This will bring into sharper relief, and prepare for 

 the study of, the distinctive characteristics of Crustacea. 



