RESULTS OF HYBRIDIZING RING-DOVES. 2Q7 



in diameter. Most of the granules are smaller than this. The 

 choroid layer in the eye of the blond bird contains large amounts 

 of the same pigment. Only minute traces of pigment occur in 

 the choroid layer of the white ring-dove, and they are found with 

 difficulty. This pigment appears to be the same as that found 

 in the choroid of the blond bird except for its scarcity. 



FIG. 3. From photograph of two nestling Fi hybrids. The smaller bird is 

 two days old, and the larger, three days. The larger bird hatched from the first 

 egg laid, and the smaller from the second egg in the same brood. The contrast 

 in size is largely, if not entirely, due to the difference in age. The larger bird 

 appears exactly like nestlings of pure blond ring-doves of the same age, and the 

 smaller like those of the white ring-dove. The picture fails to show the great 

 contrast in skin color which these birds exhibit at this stage. The smaller bird 

 is very much lighter in color than the blond form, but the photograph failed to 

 show this because the color of the skin has little actinic value. 



The pigment epithelium in the eye of the blond bird is richly 

 supplied with slender rod-shaped granules of melanin pigment 

 (see Fig. 2, A}. These granules are similar in appearance to 

 those which are seen in the feathers of many birds but they differ 

 from those of the ring-dove feather. In the white bird the 

 pigment epithelium of the retina is almost devoid of pigment. 

 A very pale brownish tint is sometimes given to the cell as seen 

 under a high power objective, which is produced by extremely 

 minute granules of what appears to be melanin pigment (see Fig. 



