STUDIES IN THE RETINA. • 47 



great preponderance of cones in young eyes, c. Shows that the transition 

 forms between rods and cones not based upon longitudinal measurements are 

 common in young eyes (see text). 



Fig. 13.— Prom a young toad. Showing the long vacuolated inner limbs 

 and short outer limbs of the rods indicative of immaturity. See Fig. 8,^, //, /. 



Salamander, Young. — Fig. 14. — Fmm a young salamander, near the 

 periphery, to show the vacuolated inner limbs and the transitional forms. 



Frog Tadpoles. — Fig. 15. — A series of elements from a very young frog 

 tadpole. Here the fact that the remains of the refractive oil globule can be 

 frequently seen in the ellipsoids of the rods proves beyond question that the 

 cones turn into rods. 



Fig. 16. — From retina of frog tadpole, showing two large sacs connected 

 with nuclei, and filling up the spaces between rods and cones (cf. the col- 

 lapsed sac in Fig. 12, a). 



