504 S. R. DETWILER AND HENRY LAURENS 
In the fully formed rod the myoid is exceedingly short. The 
presence of a narrow refractive disc between the outer and inner 
segments is demonstrable in most of the rods. In others it ap- 
pears to be lacking. 
Owing to the greater growth of the rods as development pro- 
ceeds, the difference in size between the cones and the rods in 
the fully differentiated retina (fig. 11) is greater than in earlier 
Fig. 11 Four rods and three single cones from retina of larva of 50 days after 
tail-bud stage. XX 1040. 
stages of development (fig. 8). The final form of the cones is 
seen in figure 11. Their shape and structure agree with the 
description given by Laurens and Williams (717). The outer 
segments are bluntly conical, and the granular material is not 
so characteristically arranged in lamellae as in the rods. As re- 
gards the inner segment, the size of the paraboloid is variable 
and is present in single as well as in both members of the double 
cones. 
