104 PIGMENTARY GROWTH AFTER ABLATION OF 



2. The early removal of the epithelial h5rpophysis induces a 

 striking disturbance, 1) in the pigmentary system, 2) in the 

 growth rate, and, 3) in the structural characteristics of most 

 of the other glands of internal secretion. 



3. The pigmentary alterations resulting from early hypophy- 

 sectomy are expressed by, 1) a diminution in the epidermal free 

 pigment; 2) a diminution in the number and melanin content 

 of the epidermal melanophores, together with an abnormal state 

 of contraction; 3) a maximal expansion of the xantholeucophores; 

 4) a partial contraction of the deep melanophores in the younger 

 larvae. 



4. The first three above-mentioned alterations in this system 

 result in and are essential to the complete formation of the 

 picture of albinism; the fourth does not materially contribute to 

 this picture. This would be suspected from the anatomical 

 arrangement obtaining in these cell layers and can further be 

 proved by various experimental procedures by which each of 

 these factors can be modified: 1) the partial replacement of the 

 epidermal melanin (effected by posterior-lobe feeding) is seen to 

 blanket partially the underljdng, broadly expanded xantho- 

 leucophores, the larvae being notably darker than their brothers 

 supplied with other diets; 2) the complete expansion or contrac- 

 tion of the deep melanophores of the albino effected by altering 

 the conditions of light and background does not materially 

 change the color of the albinous larvae, and conversely the con- 

 traction of these cells in the normal by the absence of light, while 

 productive of a translucency, does not produce an albino; 3) a 

 contraction of the xantholeucophores of the albino as exhibited 

 by an albinous graft to a normal host or by the use of a strong 

 anaesthetic not only results in their darkening, but in the loss 

 of the metallic silvery tone characteristic of the picture of al- 

 binism. 



5. A developmental study of the pigmentary system of the 

 albino reveals the fact that the epidermal melanophores appear 

 at a later date and in diminished numbers as compared to the 

 normal; that the free epidermal melanin suffers a relatively 

 greater diminution than in the normal, and that the xantho- 



