CHANGES IN THE VISUAL CELLS OF THE FROG 



433 



salamander where the differences in length were more striking. 

 Arcoleo ('90) and Garten ('07) reported similar conditions for 

 the toad and frog respectively. 



In most accounts oif the changes occurring in the anuran rod, 

 due to the action of light, reference is not made to the number 

 of individuals experimented upon, and in no case are definite 

 measurements of length given, judgment of the eye apparently 

 being the only critorion adopted. 



prs. dst. bac. rb. 



Fifj;. 2 Fri)in a li^lit-:ulai)t(Ml retina of the frojr, Hana pipicns, showiiiK 

 positions assunicil Ky tlie rods ami eoncs. X 1130. 



In the experimentation which forms the basis of this paper, 

 an attempt has been made to correlate an influence of light with 

 the following possible changes in the frog's visual rod: 1) changes 

 in the position of the red rod nucleus with respect to the external 

 hmiting membrane; 2) changes in the length of the red and green 

 rod myoids; 3) relati\'e changes in the length of the red rod myoid 

 at the center and at the perij^hery of the retina; 4) changes in the 

 diameter of the various comi)()nent parts of the red rod. 



