

456 SCIENCE PROGRESS 



narrow, tongue-like process, projecting forwards from the 

 main body of the hypophysis, almost to the optic chiasma. 

 Baumgartner (i) describes the derivation of this lobe from the 

 portion of Rathke's pouch lying anterior to the duct. 

 Tilney (23) states that its development and relations prove it 

 to be a true pars tuberalis. Further observations on the 

 comparative anatomy and embryology of the pars tuberalis 

 are, however, desirable. 



The dorsal and ventral lobes appear to correspond respec- 

 tively to pars infundibularis and pars distalis (P.D.), but there 

 is not a well-marked line of separation between the two 

 portions. 



The " anterior lobe " (pars tuberalis ?) appears to consist 

 of columns of epithelial cells and retains a considerable rem- 

 nant of its original lumen. The ventral lobe (pars distalis) 

 was described by Haller (6) as being a tubular gland, but 

 Herring (8) confirms Gentes' (4) view, viz. that the so-called 

 tubules are blood spaces with the gland cells arranged around 

 them. Herring (8) states that there is no differentiated " pars 

 intermedia" in Raja batis. Stendell (19), however, figures a 

 solid mass of lightly staining cells closely investing the nervous 

 portion in Scyllium canicula and in Raja asterias, and there 

 is no doubt that the portion of the dorsal lobe which lies in 

 contact with the nervous tissue differs histologically from the 

 rest of the gland. Herring (8) states that there is no differen- 

 tiation of chromophilic and chromophobic cells in the epithelial 

 lobe as a whole, but Baumgartner (1) states that in Acanthias 

 the anterior and inferior lobes may be considered the chromo- 

 philic ones. 



The development of the hypophysis in Acanthias has been 

 fully described by Baumgartner (1). A hollow hypophysial 

 invagination is formed, and in a 28 mm. embryo the primordia 

 of all the various lobes are recognisable as distinct outpouchings. 

 From these arise glandular outgrowths which Baumgartner 

 describes as being hollow in the anterior and inferior lobes and 

 solid in the superior lobe. 



Teleostomi. — Stendell (19) states that there is no group of 

 Vertebrates in which the hypophysis shows so much variation 

 as in the Teleostomi. 



The nervous lobe is well developed and generally consists 

 of branching processes, closely surrounded by epithelial cells 



