THE HYPOPHYSIS CEREBRI 463 



whether this is merely due to slight variation from the normal 

 development or indicates a common origin of the preoral gut 

 and hypophysis, as suggested by Nusbaum. It must there- 

 fore be admitted that the phylogenetic significance of the 

 hypophysis remains an unsolved problem. 



Description of Figures 



The accompanying diagrammatic figures are made partly 

 from the figures of Herring, Stendell, and Tilney, and partly 

 from my own observations. 



Fig 1. Median longitudinal section through the hypo- 

 physis of a Cyclostome. 



H.R. Hypophysial recess. O.C. Optic chiasma. P.D. Pars 

 distalis, chromophilic region. P.D.i, Pars distalis, chromo- 

 phobic region. P.I. Pars infundibularis. P.N. Pars neuralis. 



Fig. 2. Median longitudinal section through the hypo- 

 physis of an Elasmobranch. 



" AL." (? P.T.), Anterior lobe, probably equivalent to pars 

 tuberalis. I.R. Infundibular recess. O.C. Optic chiasma. P.D. 

 Pars distalis. P. I. Pars infundibularis. P.N. Pars neuralis. 

 S.V. Saccus vasculosus. T.C. Tuber cinereum. 



Fig. 3. Longitudinal section through the hypophysis of 

 an Amphibian, passing through the lateral pars tuberalis. 



P.D. Pars distalis. P.I. Pars infundibularis. P.N. Pars 

 neuralis. P.T. Pars tuberalis. 



Fig. 4. Median longitudinal section through the hypophysis 

 of a Mammal. 



I.R. Infundibular recess. L. Lumen. O.C. Optic chiasma. 

 P.D. Pars distalis. P.I. Pars infundibularis. P.L. Posterior lobe. 

 P.N. Pars neuralis. P.T. Pars tuberalis. 



Literature References 



1. Baumgartner, E. h.., fourn. of Morph. September 191 5. 



2. ibid. vol. xxviii. No. i, 1916. 



3. Burckhardt, R., Das Centralnervensystem von Protopterus annectens, 



Berlin, 1892. 



4. Gentes, L., Compt. rend, de Se'anc. de la Soc. de Biol. T. 63, 1907. 



5. Gisi, J., Das Gehirn von Hatteria punctata. Dies. Basel, 1907. 



6. Hauler, B., Morph. Jahrb. Bd. xxv. 1898. 



7. Herring, P. T., three papers in Quart. Journ. of Exp. Phys. vol. i. 1908. 



8. ibid. 1913. 



9. Howell, fourn. Exp. Med. 1898. 



10. Kerr, Graham, Quart, fourn. Micr. Set. vol. xlvi. 



