260 Frederick Tilney, 



have thus far heen examined. One notable exception must he made 

 in the case of Amia calva, for here, according to Prather [5], the 

 dorsal evagination arises entirely from the entoderm of the foregut. 

 In general, however, the hypophysis may be considered as composed 

 of two parts, the pars neuralis and the pars buccalis; the latter 

 representing the glandular portion of the body. The pars neuralis con- 

 sists of three distinct elements; namely, the eminentia saccularis of 

 the tuber cinereum, the infundibulum and the infundibular process. 

 The pars buccalis seu glandularis consists of two elements, namely, 

 the pars juxta-neuralis in close relation with and investing the neural 

 portion and the pars distalis, more remote from the neural portion. 

 In most species the pars distalis is, to some extent, separated from 

 the pars juxta-neuralis by a cleft or ventricle. This latter is the 

 remnant of the original spacious cavity of the evagination from the 

 mouth. For this reason it is termed the residual lumen. 



Further analysis of the juxta-neural portion of the gland shows 

 that histologically and topographically, it consists of two parts. One 

 of these completely invests the infundibulum and infundibular process, 

 the pars infundibularis. The other part surrounds the eminentia 

 saccularis of the tuber cinereum and because of its close relation to 

 the latter protuberance may conveniently be termed the pars tuberalis. 

 So far as a I am able to ascertain the pars tuberalis has not been 

 described heretofore. 



The usual descriptions of the tuber cinereum are not sufficiently 

 explicit in the'r detail to give a clear understanding of the relations 

 existing between this part of the diencephalic floor and the pituitary 

 gland. Eetzius [.^J, to whom we are indebted for the most exact 

 analysis of this region, describes the tuber cinereum as a protuberance 

 situated in the optico-peduncular space, immediately caudad of the 

 chiasm and cephalad of the corpora maraillaria.- Its lateral boundaries 

 are formed by the optic tracts and cerebral peduncles. The pro- 

 tuberance itself presents two symmetrical lateral swellings, the emi- 

 nentiae laterales. A third swelling, which is medial in position and 

 saccular in form, is calle'd the eminentia saccularis. The eminentiae 

 laterales are solid and less protuberant than the eminentia saccularis; 



