70 PIGMENTARY GROWTH AFTER ABLATION OF 



abnormal position of the neural lobe.'^ Indeed, this malfor- 

 mation is not limited to the neural lobe, but is participated in 

 also by the floor of the infundibular process. This floor, nor- 

 mally of considerable thickness, is membranous and folded in 

 the albinous larvae. '= 



It is of considerable importance, in view of the conditions 

 obtaining in the albino, to have clearly in mind the parts of the 

 infundibular process together with their structure in the normal 

 animal, and more especially that of the apical and ventral por- 

 tions. The walls of this process have three divisions i''' 1) a 

 ventromedial portion in contact with the pituitary gland, the 

 'pituitary' wall or floor; 2) a dorsal portion, the 'saccular' wall; 

 and, 3) the lateral extensions of both these walls which form 

 the shallow lateral concavities, the 'lateral processes.' The 

 neural lobe in its early stage develops near the apex of the in- 

 fundibular process, and in its fully formed condition is readily 

 identified as a distinct element attached by a broad surface to 

 the dorsal wall of the infundibular process, near its ventral 

 border (fig. 25). An examination of the three portions of the 

 infundibular process of the normal animal reveals the fact that 

 these regions are of two structural types. One type, that ex- 

 hibited by the lateral processes and saccular wall, is mem- 

 branous and composed of a squamous ependyma with little or 

 no ectally placed neuropilem. The other type, that forming 

 the pituitary wall, is thickened and composed of a high columnar 



'* The reduction in the size of the neural lobe in the albino was reported in The 

 Anatomical Record. In the present paper more comprehensive data have been 

 given. 



^^ The hypophysis of an anuran larva, in common with other vertebrates, con- 

 sists of four components, three arising from oral ectoderm, one from the infundibular 

 process. The development of those lobes derived from the buccal rudiment (the 

 pars intermedia, the pars glandularis and its paired cephalic processes, the pars 

 tuberahs) conforms in general to that recently described by Atwell for R. pipiens. 

 Wax models, X133, of the pituitaries of nine normal larvae, from 17 mm. in length 

 to the young adult stage have been made (table 6). In addition to these, the neural 

 lobes of ten albinos, ranging in size from 16 to 51 mm., and the neural and buccal 

 lobes of nine partial albinos were modeled. The lobes of the pituitary are readily 

 identified and their relationship to each other is constant (fig. 25, a, b, c), compare 

 to Atwell's figure 13, page 81, but considerable variation in their relative size is 

 shown. 



'^ The terminology is essentially that of Tilney ('15). 



