Kingsbury, Encephalic Evaginations in Ganoids. 39 



one fish as a small mass of cells lying to the left of the epiphysis 

 (epiphysis II). In adult Aniia, however, this structure persists 

 as a hollow vesicle closely applied to the left of the epiphysis 

 (Epiph, II) and with it enveloped by the dorsal sack in which 

 they are suspended as by a fold. Epiphysis I lies almost di- 

 rectly dorsad of the supracommissure and receives a strong fas- 

 ciculus of non-medullated fibers from the left habena (Fig. i). 

 This point is important since it strengthens the homology of 

 this with the parapineal organ (Studnicka) of Pctromyzon which 

 has been found to have fiber connection with the left habena.^ 



Lcpidosttms (adult) was examined and no trace of the epiphy- 

 sis I was found although a small cluster of cells in the proper 

 location possibly represented it in much reduced state (as in 2 

 year Salmo, Hill). No trace of it has been found in adult Poly- 

 odon or Acipenser, in which this region was subjected to exami- 

 nation by Studnicka '96 and Goronowitsch. Kupffer does not 

 show it in embryo Acipenser. 



Do7'sal Sack. Goronowitsch, I believe, was the first to 

 employ this term. It has since been employed by Mrs. Gage, 

 Herrick, Humphrey and Wilder, and seems preferable to the 

 other terms applied to this region of the brain, which seems 

 worthy of a distinct name, whatever its morphologic value. ^ 

 It is the cavity included beneath the diatela caudad of the vel- 

 um transversum, Kupffer. In Ganoids, especially the sturge- 

 ons, it is voluminous, and as described above, in Amia it envel- 

 opes the epiphysis which thus appears suspended in it by a 

 mesal fold. It does not seem to be a true evagination, such as 

 the epiphysis and paraphysis, but a dorsal extension of the dia- 

 coele, due perhaps entirely to mechanical causes and given the 



1 The suggestion of Locy that the difference in size between the left and 

 right habenas was due to this innervation, fails, since it it the right and not the 

 left which is the larger, and whatever the cause of this, it is associated with a 

 similar difference in the Meynert's bundles springing from them. This peculiar 

 asymmetry in Petromyzon also exists in Amia. 



* Synonymy; Zirbelpolster, Burckhardt ; Parencephalon, Kupffer; Postpar- 

 aphysis, Sorensen ; Vesicle of the Thalamencephalon, Parker and Balfour ; Re- 

 cessus praepinealis, Ley dig (?), 



