DETLEFSEN 



Photographs of Male Skulls in Parent Species anli Hybrids. 



1.0. r?/, original wild male ancestor o( all 12. (J'lO, one-half wild hybrid. 



wild and hybrid animals in 13, J75/, one-quarter wild hybrid, 



these experiments. ^^ ^o^^_ one-eiRhth wild hybrid. 



1.1. c^S6, male guinea-pig. 



NOTE. These and all other productions of skulls and bnnes are natural size, and as near the calculated 

 averages as possible, 



