DIFFERENTIATION OF RETINAL ELEMENTS 57 



They have been regarded by Cameron as pigment from the 

 pigment epitheUal layer ingested under the influence of the 

 original globule. Our observations are not in support of this 





Fig. 38. Cones and rods from an Amblystoma larva at stage 44 (just prior 

 to the feeding stage) showing contraction of the cone myoids in the Hght (A) 

 and elongation of the cone myoids in the dark (B). The rod myoids fail to 

 show any differences between the light-adapted condition (C) and the dark- 

 adapted condition (D). X 1030. (From Detwiler, 19235, ./. Comp. Neur., v. 36.) 



contention, for there are protoplasmic buds without the 

 globule which possess the granules. 



Leplat (1913), who studied the development of rods and 

 cones in the chick, also described deeply staining granules 



