PIGMENT CHANGES IN ANUEAN LARVAE 129 



large culture of bullfrog larvae, where there is unequal distribu- 

 tion of light and shadow, certain individuals with more or less 

 expanded melanophores of both epidermal and subepidermal type. 

 When these dark tadpoles are examined, it is found that the 

 pigment reticulum, though present, is not so dense as in the 

 engrafted animals. In such larvae the dark pigmentation is 

 temporary, and the expansion of the melanophores fluctuates 

 with changes in the evironment. Such is not the case with en- 

 grafted larvae, for when they turn dark, the expansion of the pig- 

 ment cells is permanent under all conditions of the environment, 

 so long as the glandular tissue remains intact and supplies the 

 necessary stimulus to the melanophores (fig. 4) . 



Not only are the subepidermal melanophores expanded to their 

 maximum extent in engrafted animals, but this expanded condi- 

 tion of the pigment cells apparently extends throughout the body 

 (fig. 10). Examination of the deep-lying melanophores, such as 

 are found in large numbers on the lungs, liver, peritoneum, peri- 

 cardium, and brain membranes, showed that the effect of the 

 engrafted pars intermedia is not confined solely to the superficial 

 pigment cells of the epidermis and corium. Pigmentary condi- 

 tions in the deep-lying organs are not so striking and clear-cut as 

 in the skin, because of the fact that in normal larvae the melano- 

 phores of these structures are usually in a more or less expanded 

 condition. If, however, the lungs of normal and experimented 

 tadpoles are dissected out and used as a basis for comparison, it is 

 readily seen that the degree of expansion of the numerous mel- 

 anophores on these organs of the engrafted animals is greater than 

 that of the normal controls. 



These observations are directly in line with those of Allen ('17) 

 on hypophysectomized tadpoles. He found that the animals 

 deprived of the epithelial portion of the hypophysis show a con- 

 tracted condition of the melanophores throughout the body. 

 That is, when the pars intermedia is extirpated, the pigment cells 

 all over the body contract and remain in this condition perma- 

 nently. Smith, however, finds in his careful study of albinism in 

 tadpoles deprived of the buccal portion of the hypophysis that in 

 young animals the subepidermal melanophores are contracted 



