ORGANIC EVOLUTION 



245 



The record. — Enumerate carefully the points of similarity 

 in the two forms compared. Then make separate lists 

 of the distinctive group characters of the two which show 

 them to belong to two different lines of development. 



Fig. 152. Wings of two living dragonflies, for comparison with fig. 151. The 

 upper, Anotogaster (family Aeschnidae) ; the lower, Orthetrum (family 

 Libellulidae). 



2. Progressive and regressive development. 



As a general phenomenon, progressive development 

 needs here no further presentation. It has been illustrated 



