PREFACE 



A VERY few words will suffice to make known 

 my object in writing the present work. 



Zoology and Botany have been looked 

 upon as constituting less practical branches 

 of Science than Chemistry or Astronomy, for 

 instance. The zoological works placed in 

 the hands of students are necessarily so full 

 of anatomical details, details of classification, 

 and observations upon the habits and in- 

 stincts of animals, that very little space has 

 (or could have) been afforded to notice the 

 wonderful manner in which certain animals 

 contribute directly to the welfare of mankind, 



