PATTEN— COOPERATION AS A FACTOR IN EVOLUTION. 519 



Fig. 4a 



A 



gst 



tu 

 B 



gst 



■-^- 



-Vt,Wr»»V>*- 



eye 



cL 



OXC 



cay c * 



2 4 tp' 



C 



..ttifiK. 



canv 



Figs. 4a and 4b. Diagrams illustrating the embryonic development of an 

 arachnid embryo and the hypothetical transition stages to one of the vertebrate 

 type. For further exlanation, see Patten, " The Evolution of the Verte- 

 brates and their Kin." 



petual readjustment of the new and the old to one another in such 

 a way as to give better organic cooperation. And because of this 

 improvement in organic cooperation, the individual organism in- 

 evitably increases in volume, in power, and in freedom. 



PROC. AMER, PHIL. SOC, VOL. LV, GO, AUG. I9, I916. 



