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Show 200 ON THE STRUOTUHE OF THE SKULL. of roue h con t roversy. In a remarkable essay pub. lished in the first volume of the "Memoires du Museum," Cuvier propoRed to consider the upper dentigerous arch (h) as the hon1ologue ?f tho palatine and pterygoid bones o~ osseous fishes, th~. cartilages ( i, 7c) as the premaxilla and maxilla. The su~pensonum (g) ~1o considered to be the homologue of the hyomandibular, symplectic, and meta pterygoid. The lower dentigerous arch ( Mn) was ob-vious! y the mandible. . . . On this latter point all anatomists are agreed; but, In lus famous " Comparative Anatomy of the Myxinoid l:!'ishes," Johannes Muller-guided, like Cuvier, by purely anatomical considerations, and by what I have elsewhere termed tho method of gradation-proposed a totally different interpret ation of the other parts. According to this view, i, k, and l are merely labial cartilages, and therefore do not represent the premaxilla and maxilla. Again, Cuvier had greatly relied upon the absence of any parts on the inner side of h which could answer to palatine or pterygoid elements, in arguing that h itself represents them. But Muller adduced his own and Henle's observations to prove that in a great many Plagiostomes, particularly the Rays, such cartilages, situated on the inner side of the upper dentigerous arch, do occur, and thus arrived, by a line of argumentation precisely as legitimate as that of Cuvier, at the exactly opposite result,-that h represents the premaxilla and maxilla, and not the palatine or pterygoid. The fact that these opposing views were entertained by men like Cuvier and Muller is evidence that each had much in its fa~our ; but, in truth, neither was free from grave difficulties. Thus neither accounted for the articulation of the mandible with the upper dentigerous arch,-a relation into which the mandible never enters either with the palatine, or with the maxilla, in the vertebrate series; and as Muller himself is forced to admit that some of the cartilages on the inner side of the upper dentigerous arch are accessory, why should not all be so? This is just one of those cases in which the study of development manifests its full importance, and decides, at once, problems which, without it, might be the subjects of interminable discus· 'rHE SKULLS OF FISHES. 201 sion. A ~omparison of the skull of the monk fish with that of the embryonic oss.eous fish (Fig. 72, C) seems to me to demonstrate beyond ~uestion, that the upper dentigerous arch (h) corresponds with the ~alato-quadrate cartilage of the embryo,* and that the suspensorium (g) equally corresponds with the h T _ ]'b 1 d . )Oman c I u ar an symplectic cartilage. But in this case Cuvior's view of t.he upper dentigerous arch must be reaarded as a singula 1 • • _. . b r y near .appioximation t? the truth, for It certajnly answers to the palatine an.d pterygoid ; though, in addition, it contains the representatives of the quadrate and meta pterygoid bones of tho osseou~ :fish. A~d his opinion regarding the nature of the suspensorium was still nearer to what I believe to be right. On the other hand, I think it very probable, though not certain th t as l\Iiiller supposed, the cartilages (i, k, l) are merely Jabi~l, a~d that .these :fishes have no representatives of the premaxilla and m~xiila.. But ~he so-called palatine and pterygoid cartilages of lVIuller, I~ the VIew I ~ake is correct, are as much accessory parts a~ th~ spuacular cartilages, and, like them, have no representatives In osseous fishes. . * .~a~l~lm. arri:ecl ~~ this co~clusion also, on developmental ground , in 1839. See Ius Vw1tei Boncht, quoted m the last Lecture of this work. |