OCT 18 1«M 



Bulletin of the Museum of Comparative Zoology 

 AT HARVARD COLLEGE. 



Vol. XXXV. No. 6. 



THE PHOTOMECHANICAL CHANGES IN THE RETINAL 

 PIGMENT OF GAMMARUS. 



By G. II. Parker. 



With < ixi; Plate. 



CAMBRIDGE. MASS., U.S.A.: 



PRINTED FOR THE MUSEUM. 



October, 1899. 



