INSECTIVOROUS ANIMALS 291 



On the side of public economy, the toad is one of the 

 most important animals we have. Toads are practically 

 at every child's door ; it need cost nothing for specimens, 

 and their commonness makes it possible for children to 

 observe and study them at odd times about their homes. 

 Further than this, the school children might save in the 

 course of their outdoor laboratory work and play from 

 $100,000,000 to $200,000,000, nearly half the expense 

 of their entire public school education, by learning and 

 utilizing this one species as a beneficent force in nature 1 ; 

 and the effect will first be felt in their own gardens. 



As an introduction to zoology no animal has a develop- 

 ment better adapted for study. The eggs are abundant, 

 come at a convenient season, and pass so rapidly through 

 the different transformations that even young children 

 do not lose interest. Nothing could be better calculated 

 to open the door of interest into comparative embryology 

 and zoology. Then there is the sleight-of-hand magic 

 of catching insects. Nothing in all the varied perform- 

 ances of animals brings so quickly : How did he do it ? 

 What did he do it with ? Such questions open the 

 way to comparative anatomy. Next we have a question 

 that will prove a puzzle. Ask the children if any of them 

 ever saw a toad drink. How did it drink ? Here we 

 have comparative physiology. A toad drinks by absorbing 

 water through the skin. 



Deprive a toad of water for a day and weigh the specimen care- 

 fully. Next let it sit on a wet blotting paper, or pour a little water 

 into its vivarium, and, after an hour, weigh the toad again. The 

 gain will represent water absorbed. 



1 Riley's estimate is that insects cause from $300,000,000 to $400,000,000 

 damage annually. 



