34 Journal of Comparative Neurology. 



connected with the saccus has the same structure as the latter. 

 'I'he epitheHum lining the prolongation of the infundibular ven- 

 tricle gives off fibres which lie adjacent to the epithelium and 

 ectad of it. 



Now returning to the drum, we observe in horizontal sec- 

 tions that the hypophysis proper is composed of two distinct 

 portions, an axial portion derived from the brain and in essen- 

 tials of structure much like the saccus which is to be regarded as 

 a separated portion of it, and an outer zone which is quite dis- 

 tinct and has exactly the structure found in the opossum. 

 There seem to be some nerve cells in the axial portion which 

 doubtless arise as elsewhere in the central system as outgrowths 

 of the epithelium. This part differs from the saccus only in its 

 denser epithelium and and more complete convolution. The 

 connection of the fibres with epithelium cells is beyond question. 

 The relation of fibres and blood vessels is identical in the com- 

 pared organs. It seems quite beyond question that these two 

 portions are homologues of the axial portion of the hypophysis 

 of Didelphys while the outer or mantle portion is derived from 

 the pharynx. 



In Carpiodes the hypophysis is well developed and the 

 saccus quite small, the development of the two seems, as might 

 be expected, to sustain ah inverse relation. The connection 

 between the very small ventricle of the hypophysis and the con- 

 voluted cavity of the saccus is direct, though a small protrusion 

 of the tuber separates them. One can trace direct connection 

 between the ventricle of the peduncle of the hypophsisand some 

 of the main diverticula. The medullary part of the hypophysis 

 is very large and contains two lateral portions of a denser char- 

 acter which may represent the outer layer of higher animals 

 although there is in addition a small envelope of the usual sort. 

 The epithelium cells can be traced into definite connection with 

 the fibres of the peduncle which also bear scattered intermediate 

 nuclei of spindle form (inoblasts). It does not seem probable 

 that there are many nerve fibers among the tracts, though their 

 presence is not excluded. The epithelium of the saccus is 

 strongly ciliated. The stalk of the hypophysis forms a sort of 

 irregular decussation or confusion of fibres after which two lateral 

 bundles collect and pass cephalo-dorsad to the latero-cephalic 



