10 PIGMENTARY GROWTH AFTER ABLATION OP 



as will be shown replaces the growth substance lost by hypophy- 

 sectomy, the albinos thrived and were much more healthy, 

 vigorous, and enjoyed a greater longevity than with any other 

 diet. This gland proved to be a very desirable food substance 

 for the normal tadpole as well. 



The alterations referable to hypophysectomy in frog or toad 

 larvae express themselves in several ways. There early appears 

 a pigmentary disturbance productive of a silvery tadpole 

 the albino. This system then exhibits profound structural and 

 functional modifications. An early retardation in growth is 

 apparent which progressively becomes more marked with devel- 

 opment. The growth curves of these animals differ not only 

 in their magnitude, but in their character when compared to 

 the normal. And finally, most of the other members of the 

 internal secretory system present a structural picture differing 

 greatly from the normal. 



It is thus convenient to present the matter under three head- 

 ings: 



Disturbances in the pigmentary system. 



Alterations in the growth rate. 



Alterations in the other glands of internal secretion. 



2. ALTERATIONS IN THE PIGMENTARY SYSTEM 



The striking color changes which many of the lower verte- 

 brates exhibit under changed environmental conditions has long 

 been known and early attracted attention to the mutual inter- 

 play of the various components of the chromatophore groups 

 by which this chromatic 'adaptability' was effected. In addition 

 to these environmental color changes, it has also been shown 

 that pronounced changes in certain of the chromatophore groups 

 can be experimentally induced: by the injection of adrenalin 

 into the frog, Lieben ('06) ; by the immersion of the entire animal 

 or portions of it in certain endocrine extracts, McCord and 

 Allen ('17), Lowe ('17), Spaeth ('13 and '18, with fish scales); 

 by experimental operative procedures, Lister ('58), Bimmerman 



