THE EVOLUTION OF ARTHROPODS AND THEIR 

 RELATIVES WITH ESPECIAL REFERENCE 

 TO INSECTS ' 



The two lines of docciit wliicli have culiiiiiinted in the 

 production of some of the most active and "dynamic" 

 of livm|2^ creatures, and those in whicli tlie psychic facul- 

 ties have attained their highest degree of perfection, are 

 rei)resented by tlie vertebrate group Mammalia, at whose 

 a])ex is man, and the invertebrate grou]) Arthropoda, at 

 whose apex are the Insecta. Since these are the great 

 rival groui)s, contending for the ])ossession of the earth, 

 the tracing of the paths ])v which thev have aiTiv(Ml at 

 their present dommariiiii' [...mIk-h- <-itl(.r<l> (.nc of the 

 most fascinating cha])t<'i'> ot the >tu(lv ot oiiiaiiK- cxolu- 

 tion. Concerning the ancestry of num. there is some 

 degree of agreement of oi)inion in modern works upon 

 the subject; but the recent investigations of Handlirsch, 

 190-J-1908, are not in accord with those of his predeces- 

 sors in the stndv of insect jihvlogenv. and since his views 

 have received a -urpn-iiiiiK- wKh'-inend acceptance, his 

 w^ork has served to rcs ivc the (h-cn->ioii of the ultimate 

 derivation of the iiisectaii tvpe of animals. 



There can he hul litth^ doubt that the insects and their 

 arthropodan relative- are the descendants of ancestors 

 related to the worin-iike forms. These m turn were de- 

 rived from h)wer worm-like ancestors resembling the 

 members of the Kotifera-Platyhelminthes group. In the 

 present state of our knowledge of the subject, it is hardly 

 possible to state with anv decrree of certainty whether 

 the ancestors of tlie woiiii-Iik(^ forms wvvo ultimately 



