34 'Journal of Comparative Neurology and Psychology. 



hypothalamus which can unmistakably be considered as infundib- 

 ulum, while the lobi inferiores have not yet, or scarcely yet, come 

 into view. Through the infundibulum the hypophysis communi- 

 cates with the third ventricle and also backward with a second 

 projection of the basis thalami, the saccus vasculosiis (Lophius, 

 Fig. xxx; Gadus, Figs, xliii to 1). 



Hypophysis and saccus vasculosus, though in connection with 

 one another and inserted upon the hypothalamus at nearly the 

 same place, are, however, genetically in no relation whatever with 

 one another. The saccus vasculosus begins as a projection from 

 this region of the hypothalamus (Edinger), while the hypoph- 

 ysis begins, according to some investigators, as an ectodermal 

 projection inward; according to others from ectodermal and ento- 

 dermal tissue, which is secondarily connected with the infundib- 

 ular region. Boeke even maintains that in Murena the ecto- 

 derm does not participate in its definitive construction and claims 

 that it originates from a meso- (ento-) dermal tissue. 



At the place of the insertion of the saccus the lateral walls of the 

 original infundibulum show an important lateral thickening, the 

 lobi inferiores of Fritsch, Mayser, Bellonci, Chatin, Ussow, 

 Edinger, Catois; the hypoaria of Sanders and Herrick. 

 Even among the earlier authors there was a difference of opinion 

 about the functions of these lobes, which Vicq d'Azyr and Tre- 

 viRANUS considered as corpora mammillaria; A. v. Haller as 

 connected with the olfactorium; Cuvier as optic lobes; Carus as 

 a continuation of the tuber cinereum, the latter opinion being 

 shared by Catois. Fritsch homologized them w^ith the corpora 

 mammillaria of the higher animals, a view which Sanders was 

 inclined to accept. With good reason C. L. Herrick points out 

 that the relations of the tracts in this region which, like Edinger, 

 I call lobus inferior, make it impossible to consider it the homo- 

 logue of the corpus mammillare, which, however, is not now 

 accepted anywhere, for the whole lobe at least. ^ 



'C. L. Herrick was the first to describe as corpora mammillaria two bilateral projections of the 

 infundibulum which regularly appear and are provided with their own ventricle corresponding with the 

 ventric. lobi inf. along which run fibers of the saccus vasculosus. They are seen in Lophius and Gadus 

 in Figs, xxx, xliv and xlv, of Plate II. After Herrick they were mentioned by David, who, however, 

 did not consider them as homologues of thecorpora mammillaria and called them "lobi mediani." 

 Johnston, who described them in Acipenser, considers that they, together with the "mid-ventral part" 

 of the lobi inferiores, constitute the corpora mammillaria. 



