No. 625] THE EVOLUTION OF ARTHROPODS 165 



attempt to derive the Pterygota more directly from trilo- 

 bites, is forced to assmiie that the lepismids may represent 

 degenerate Pterygota! Their whole stnrctiiral organiza- 

 tion clearly proclaims in no uncertain terms that the 

 closest affinities of the lepismids are with the rest of the 

 Apterygota, with which they are connected by inter- 

 mediate forms, and a careful study of the comparative 

 anatomy and embryology of the A])torygc)ta, " Myrio- 

 poda" and Crustacea can result in no othei- conclusion 

 than that the Apterygota have de|)arted as little as any 

 known forms from the condition characteristic of the an- 

 cestors of the Pterygota. The lepismids are therefore no 

 more to be considered as degenerate Pterygota, than apes 

 are to be considered as degenerate men— unless one re- 

 verses the whole scheme of evolution; and under such 

 conditions there would be nothing to prevent any one from 

 assuming that trilobites are degenerate lepismids, or any 

 other equally improbable reversing of the evolutionary 

 sequences ! 



In connection with the supposedly degenerate" con- 

 dition of the Ai)terygota. 1 would take issue with the im- 

 plication carried in sudi >\i\truwn{< as that by Totliill, 

 lino (]). ;]7(i), who would claim tiiat the A ptci'v-ota ''are 

 highly spcfializcd animals as iiidicatrd b\- the t'rr.iucut 

 reduction of mouth parts, visual oruaiis. trachen'. etc.; 

 and by the development of ptM-uliar structures sucli a- the 

 caudal spring and collopliorc. In. tlic first |ilacc. it is 

 inadmissible to judge the ancotral character of any 

 groui> by the condition of it- mo>t highly specialized 

 memhcrs. as Tothill apitears to do in the case of the 



low it may bo in the sc.-de of develoi-ment {r. r/., Cope- 

 poda. etc.) niav include certain nieniheis which have be- 

 come very higlily spociali/ed along theii- own lines of de- 

 velo])ment without affecting the genei'al position of the 

 group as a winkle: and in a phylogenetic study we must 

 consider the most juimitive repre>entatives of the group, 

 rather than the nio>t highly >pecialized ones, if such a 

 studv is to vield anv tangihU^ roults. If Tothill had 



