302 Natural History Bulletin. 



7. The diverticulum of the alimentary canal disappears, 

 but the pituitar}^ body is formed from the mesoblast in front 

 of the clinoid process. 



Rathke, Entzvichlungsgeschichte der Wirhelthiere^ Leipzig, 

 1 861. (Original not in hand.) 



8. The formation of the hypophysis is mechanical, due to 

 the cranial flexure constricting off a wedge-shaped portion of 

 the alimentary canal. 



Wilhelm Mueller, yenische Zeitschrift,Yid.Yl, i^"]!. (Origi- 

 nal not in hand.) 



9. The hypophysis arises not from the closed foregut, 

 lined with hypoblast, but from the buccal cavity Hned with 

 epiblast. 



Goette, Archiv. Micr. Anat., IX, p. 397. (Original not in 

 hand.) 



Comparative Embryology, Balfour, 1880, Vol. 11, p. 358. 



Human Embryology, Minot, 1892, p. 571. 



Gray's Anatomy, 1887, p. 120. 



Introduction to Stud}- of Embryology, Haddon, 1889, p. no. 



Elements of Embryology, Foster and Balfour, 18S9, p. 119. 



Quain's Anatomy, 1890, pp. 68 and 100. 



Thus each of the three layers of the blastoderm has been 

 described as forming the hypophysis cerebri. The end of the 

 notochord, and even the pia mater, has been thought to give 

 rise to this structure. What may be called the mechanical 

 theory at one time prevailed, and is not entirely abandoned 

 even now. (Human Embryology, Minot, 1892, page 574-) 



METHODS. 



The technique employed in 1889 during these investiga- 

 tions would now be considered somewhat antiquated, but 

 the results compare favorably with those obtained by more 

 refined methods. 



The embryos were hardened in increasinc;' strengths of 



