THE KINSHIP OF LIFE. 



35 



of heredity. If, however, man possessed no " blood re- 

 lationship " to three-eyed vertebrates, the existence of 



Fig. 3. — Head of the lizard, or " horned toad " {Phrynosoma Main, 

 dillei), showing the translucent pearly scale covering the pineal eye. 

 From Nature, by W. S. Atkinson. 



the pineal body in the human brain would be wholly 

 inexplicable. 



It has been difficult to explain, on the theory of de- 

 scent, how complex organs like the eyes and ears of the 

 higher animals could develop from small 



Origin of com- beginnings. To embryology we must 

 plex structures. 00 j oj 



look for explanation. Embryology tells 



us that these organs do not in the individual reach per- 

 fection "all at once." In every case the embryonic his- 

 tory of a highly specialized organ shows a succession of 



