INTRODUCTION. 5 



zoological tasks, attained importance as a scientific aid to geology, 

 since it furnishes the materials for characterizing and fixing the 

 various geological ages and the earth's history during those ages. 

 When, therefore, at the present day we speak of zoology, we 

 usually refer to morphology and classification of living animals 

 with consideration of their general vital phenomena. 



The views here given of the character of zoology have not been 

 the same in all time. Like every science zoology has developed 

 gradually; it has varied with each epoch and tendency, according 

 as the systematic or the morphological or the physiological point 

 of view was the prevailing one. It will now be interesting to take 

 a hasty glance at the most important jjhases in the development 

 of zoology. The reader will better understand the questions which 

 now dominate zoological inquiry, if he know how these have arisen 

 historically. 



