No. 536] 



COLOR INHERITANCE 



457 



brown color of the melanic granules. These results from 

 experimental procedure are confirmed by findings in the 

 retina of the calf embryo, where the identical stages in pig- 

 ment formation are observed. He thinks it more probable 

 that the pigment has origin in an albuminous substance 

 (this is in complete accord with the work of Chittenden 

 and Albro— 1903) of the nucleus than that haemoglobin 

 has any contributory role. The earlier stages in such a 

 process can be observed in carcinoma without progress to 

 the final stage of pigmentation. This indicates that we 

 are probably dealing with a nuclear substance, which, shed 

 into the cytoplasm, under the influence of an oxidation 

 enzyme, becomes a melanic substance. 



As bearing on the point of the origin of pigment my 

 own observations are as follows : No undoubted branching 

 pigmented cells can be seen among the colored epidermal 

 cells in any of my specimens. Occasionally a process of a 

 pigmented connective tissue cell of the cutis is seen to 

 extend for some distance into the rete mucosum Malpighi 

 (Fig. 1 ). But their number seems very much too meager 

 to supply the pigment of the many colored cells of the 

 epidermis. There is a nice correspondence between the 

 relative abundance of pigmented cells in the dermis and 

 epidermis of the several specimens of skin. In light skins 

 there are few of each type in each layer; in darker skins 

 there is a decided increase in both. But this proportional 

 increase is as reasonably interpreted as due to the same 

 cause influencing both layers, as that the increased number 

 of pigmented epidermal cells demands an increased 

 number of cutis melanoblasts. Moreover, when one con- 

 siders that there is a continual exfoliation of the super- 

 ficial layers and a replacing of the same from the lower 

 layers, the number of epidermal pigmented cells in colored 

 skins seems out of all proportion to the number of the 

 cutis melanoblasts which are supposed to furnish the 

 pigment. 



The pigment cells of the cutis are most abundant along 

 the border between dermis and epidermis and along the 

 capillaries of the vascular papillae. This first point would 

 seem to indicate the function ascribed to them by Karg 



