162 NATURE STUDY. 



apex of each division of a leaf. We see here another 

 reason for emphasizing the "why" in nature study. 



Third. That which is most important, and should 

 therefore be remembered, must be frequently repeated or 

 reviewed. Here we see the necessity for drill. Because 

 of the first law of memory, stated above, the review will 

 be most effective when the images are fresh and clear. 

 Because of the second law, that review is best which 

 emphasizes relations and not merely facts. Hence each 

 lesson should close with a summary, gathering up, bring- 

 ing together, and relating the important points brought 

 out. The first step in each lesson should, in general, be 

 a review of the previous lesson or lessons, or at least of 

 those portions of previous lessons on which the new 

 work depends. So, also, each step in a lesson should 

 be reviewed and stated clearly before passing to an- 

 other step. This summary tests the clearness of the 

 impressions, brings out the relations of the ideas or 

 facts, and helps to fix them in the mind by having 

 them repeated. 



Constructive imagination, or imagination proper as 

 distinguished from memory, differs from the latter in 

 that it not merely repeats the mental images of what 

 has been seen or perceived, but takes from, adds to, 

 combines and recombines them, forming a picture of 

 what has not been seen. It is only through imagination 

 that we are able to become -acquainted with that great 

 part of the universe of which our senses alone give us 

 little direct knowledge. It is imagination which helps 



