. The Journal of comparative neurology and psychology. ge, Sterzi, and others),but not by all. I wish to emphasize the necessity of recognizingthe two pits and applying to them clearly distinctive names, becausethey are both related to the optic vesicle and because the postopticrecess has heretofore been confused with the infundibulum. b. Remainder of the Floor of the Diencephalon.—As soon as thehead-bend of the brain tube appears, a broad depression of the floorof the forebrain vesicle can be seen which corresponds to the future Johnston, Forebrain Vesicle in Vertebrates. 483 inferior lobes (
. The Journal of comparative neurology and psychology. ge, Sterzi, and others),but not by all. I wish to emphasize the necessity of recognizingthe two pits and applying to them clearly distinctive names, becausethey are both related to the optic vesicle and because the postopticrecess has heretofore been confused with the infundibulum. b. Remainder of the Floor of the Diencephalon.—As soon as thehead-bend of the brain tube appears, a broad depression of the floorof the forebrain vesicle can be seen which corresponds to the future Johnston, Forebrain Vesicle in Vertebrates. 483 inferior lobes (Fig. 16). The anterior part of this is the relativelydeep and sharply marked primitive optic groove. The posteriorlx)iindary is less definitely marked by a slight projection of the brainfloor into the ventricle. This is the tuberculum posterius. As thebroad inferior lobes involve nearly the whole floor of the diencephalon,neither the infundibulnm nor the mammillary bodies are to berecognized at this time. Both are developed later within the general. Fig. 19. Sqiialus ac, GO somites, parasagittal section near the middle mouth is open. Primitive inferior lobes, epiphysis and velum 33. area of the primitive inferior lobes, as specialized portions of theirwalls. The mammillary bodies are indicated by a rounded caudal pro-jection of the depressed floor of the diencephalon in embryos withabout 80 somites (Figs. 20, 21, 22). The infundibular recess is not found until after the completionof the changes described in connection with the optic recesses. Asin man the infundibulnm is the funnel-shaped depression leadingfrom the floor of the tuber cinereum into the neural part of the 484 Journal of Coinparative Neurology and Psychology. pituitary body, so in fishes the infundibular recess must be thatsomewhat funnel-shaped or trough-shaped depression in the floorof the inferior lobes which leads into the saccus vasculosus, thisbeing the neural portion of the pituitar
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