6. THE ORIGIN OF A POLYDACTYLOUS RACE OF 

 GUINEA-PIGS 



BY 



W. E. CASTLE 



PAPERS OF THE STATION FOR EXPERIMENTAL EVOLUTION AT COLD SPRING HARBOR, 

 NEW YORK, No. 6 



CONTRIBUTIONS FROM THE ZOOLOGICAL LABORATORY OF THE MUSEUM OF COMPARATIVE 

 ZOOLOGY AT HARVARD COLLEGE. E. L. MARK, DIRECTOR. No. 176 



