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 



