82 PIGMENTARY GBOWTH AFTER ABLATION OF 



the thickened wall characteristic of the pituitary floor of the 

 normal specimens. If freed from the influence of its buccal 

 associate and left to its own independent development, the 

 membranous structure persists; under the stimulatory influence 

 of its buccal associate, a thickening results, leading to the solid, 

 firm structure of the normal tadpole. Curiously, in the absence 

 of the buccal hypophysis, the inherent capacity for growth 

 expresses itself in the neural lobe as if an hereditary influence 

 here exerts itself and leads to the formation of a 'vestigial' 

 structure. That the epithelial hypophysis does exert a stimu- 

 latory effect upon the adjacent neural tissue seems clear, as 

 has been pointed out, not only from the evidence accruing from 

 a study of the albino in its different stages, but from the 'partial ' 

 albino as well. The diminutive and misplaced fragment of the 

 buccal hypophysis in these specimens has invariably formed 

 about itself a brain lobe, identical in structure, so far as can be 

 determined, with the normally placed pars nervosa of the pitui- 

 tary. Moreover, the 'influence' of this vestigial epithelial gland 

 appears to be effective at some distance, as indicated by certain 

 specimens which, in sharp contrast to the albino, have no apic- 

 ally placed neural lobe. This condition suggests that this lobe 

 has either been inhibited and a new atypically placed lobe formed 

 de novo or it has been attracted to a new position by this mis- 

 placed epithelial fragment. 



The inherent capacity for growth existing in the three por- 

 tions of the infundibular process and the response of these por- 

 tions to the presence or absence of the buccal component of the 

 hypophysis can perhaps best be shown by schematic curves 

 illustrating the reaction of the pituitary floor and one of the 

 other portions of the infundibular process under the two con- 

 ditions of normality and buccal hypophysectomy (fig. 10). 

 These curves show the development of the pituitary wall in a 

 normal tadpole and its albinous mate, together with a third 

 curve showing the development of the dorsal and lateral walls 

 of the infundibular process in either normal or albinous tad- 

 poles. 



