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SCIENCE PROGRESS 



The nervous portion is very slightly developed. There is 

 a wide and shallow depression of the diencephalic floor (fig. i), 

 the hypophyseal or infundibular recess (H.R.), whose wall 

 is not thickened to any marked extent. Herring (8) states 

 that the wall consists chiefly of ependyma cells placed with 

 their long axis vertical to the internal surface and stains rather 

 more deeply than the rest of the brain wall. This pars neuralis 

 (P.N.) is closely invested by a layer of deeply staining epithelial 

 cells, constituting the pars infundibularis (P.I.), which does 

 not penetrate into the pars neuralis. 



The pars distalis (P.D.) lies anterior to the pars infundibu- 



FlG. I. 



laris, from which it is separated by a thin layer of connective 

 tissue. It consists of two portions, the chromophil and 

 chromophobe portions of Sterzi. The anterior of these con- 

 sists, according to Herring, of solid, irregularly arranged 

 columns of large, granular cells, which take up most stains 

 readily. The posterior portion consists of columns of cells, 

 fairly regularly arranged, and showing little affinity for stains. 

 Both portions are richly vascularised and the line of division 

 between the two is well marked. 



Stendell(i9) describes the development of the hypophysis 

 in Cyclostomata, quoting von Kupffer (11) and Sterzi (20). 

 The hypophysial and olfactory primordia arise from a common 

 invagination. The caudal portion of this represents the pri- 



