78 PIGMENTARY GROWTH AFTER ABLATION OF 



(fig. 30), a condition which strongly suggests that the neural 

 Lobe had migrated cephalically and was attempting to assume 

 a juxtaposition with the unusually placed epithelial fragment. 

 This seems the more probable, since in the specimens which have 

 suffered a complete loss of the epithelial hypophysis there is 

 always a readily distinguishable neural lobe. That the epi- 

 thelial hypophysis apparently exhibits not only this 'attractive' 

 force upon the neural lobe, but definitely stimulates the growth 

 of adjacent neural tissue, is shown both by the thickening of 

 the neural tissue about the epithelial hypophysial vestige 41 in 

 the partial albinos and by the negative evidence supplied by the 

 absence of the usual thickening of the pituitary floor and dimin- 

 ished size of the neural lobe in the albino which displays no 

 epithelial hypophysis whatever. It thus seems clear that in 

 the absence of a nearly normal epithelial component the neural 

 hypophysis cannot undergo its normal development nor attain 

 its typical shape or size. 42 That the neural lobe can and does 

 form even in the absence of its associate, however, is clear, and 

 it seems equally clear that in those specimens in which a suf- 

 ficient metamorphic stimulus is supplied, whether by the thyroid 

 or the hypophysis or jointly, that this lobe can attain a very 

 considerable size. 43 



11 Although this neural lobe simulates in structure the typical lobe, nevertheless, 

 it seems doubtful whether it is able to assume the functions of that lobe. That 

 it can assume this function appears improbable both from the failure of such speci- 

 mens to metamorphose as well as from the serious pigmentary disturbance which 

 they display. 



12 To what an extent the general disturbance in this correlative system of organs 

 plays a part is problematical. It is difficult to determine, save by grafts of the 

 buccal component with the hypophysectomizcd larvae, an undertaking which has 

 not been fruitful in the hands of the author. A similar failure to secure significant 

 effects lias recently been reported by the Hoskinses. Likewise, efforts to secure 

 an apposition of the buccal component and the lateral or dorsal walls of the in- 

 fundibular process have so far failed. The author hoped to determine by such 

 misplacement of the buccal component whether these walls would undergo the 

 hypertrophy normally exhibited by the pituitary wall. 



43 No clear evidence is at hand showing whether the buccal lobe would undergo 

 a normal development in the absence of its neural associate. Suggestive evidence, 

 Imwcvcr, that it can develop independently is furnished by the work of Haberfeldt 

 ('()9). According to this author, the pharyngeal hypophysis, although far remote 

 from any neural associate, parallels in development and differentiation the pars 

 glandularis of the hypophysis. 



