308 NATURE STUDY. 



Other things being equal, the buttercup is much 

 better as a type of the crowfoot family of flowering 

 plants than is the columbine ; the cranesbill is better 

 than the " touch-me-not " as a type of the geranium 

 family. The grasshopper is better as a type of insects 

 than is the butterfly, although the butterfly may be bet- 

 ter than the grasshopper for the study of life history or 

 development. 



This idea of the importance of studying types leads 

 to the selection of such material as horsetails and ferns, 

 rather difficult for study, and of corals, starfish, and 

 sponges, which must almost always be studied from 

 dead specimens and pictures. But they are important, 

 in work with older pupils, because they are types of 

 great classes of which the pupils should know some- 

 thing. 



The laws of sequence and unity largely determine the 

 selection and arrangement of material and the formu- 

 lation of a course of study. It is essential that the 

 material be so selected and arranged that there is a 

 natural logical sequence, that each topic shall be con- 

 sidered with reference to what precedes and follows. 

 The course in any one line of study plants, animals, 

 minerals, physics should be a connected whole built 

 up step by step. The work in all lines should be re- 

 lated and made mutually helpful as far as possible. 

 New topics should not be undertaken until the foun- 

 dations have been laid for their study by gaining the 

 knowledge necessary for their comprehension. Lime- 

 stone and fossil shells mean little until the children 



