. Notes on the North American ganoids [microform] : Amia, Lepidosteus, Acipenser, and Polyodon, with three plates. Ganoidei; Fishes; Ganoide; Poissons. 180 B. NATUBAL HISTORY. f: ^1 k- \ tho brain behind the cmra thalami. These latter nocm to corres- pond to tlie thalami of the higher Vertebrates; tho third ventricle lies between them, the conarium above and the hypophysis below. Aside fVom the adverse opinions of all authors (which, however, are of less importance in view of the imperfection of tlio material at their disposal) the only objection to this view is, that it makes the hemispheres
. Notes on the North American ganoids [microform] : Amia, Lepidosteus, Acipenser, and Polyodon, with three plates. Ganoidei; Fishes; Ganoide; Poissons. 180 B. NATUBAL HISTORY. f: ^1 k- \ tho brain behind the cmra thalami. These latter nocm to corres- pond to tlie thalami of the higher Vertebrates; tho third ventricle lies between them, the conarium above and the hypophysis below. Aside fVom the adverse opinions of all authors (which, however, are of less importance in view of the imperfection of tlio material at their disposal) the only objection to this view is, that it makes the hemispheres so much smaller than cither the thalami or the olfactory lobes. It is to be remembered, however, that mere size is of no value for tho determination of homologies. The cerebellum is recognized as such in the lamprey and the salamander because it is a bridge over the fourth ventricle, although it is "o much smaller than the corresponding organ of the bird oi' mammal. The hemispheres are hardly larger than the optic lobes in some Batrachians, while in man they overshadow all the other parts. Now the hemispheres are, by development, mere buds fk-om the thalami, yet, as may happen with human families, the offspring are larger than the parents. In like manner, in the Ganoid brain, the hemispheres themselves are surpassed in size by their buds^ the olfactory lobes. ,.t .., But while regarding the view here advanced as based upon sound morphological grounds, the large size and convoluted surface of the thalami suggests the idea that they may in some way /unc- tionally represent the hemispheres. For the determination of this the brain should be examined microscopically and the fibres from the medulla should be traced forward into the several lobes as has been done with the ftog by Wyman and Stieda. They should also be experimented upon by injury, ablation and galvanic stimulation. To complete the evidence we should find, at least in young spec- imens, something like a lamina termi
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectfishes, bookyear1876
