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Show 1891.] ORGAN IN THE CROCODILIA. 155 maxillae is effected. He asserts that in some pf the forms he examined he regarded the anterior paired vomers as the sole representatives of the palatine processes of the preinaxillae. In describing some embryos, his language is onlv to be so construed as to show that he regarded the latter as representing (Erinaceus, p. 149, Talpa, p. 179, Galeopithecus, p. 253) a fusion of true palatine spurs of the premaxillae with his anterior paired vomers so often alluded to. In having declared that in the Mole the " anterior paired vomers . . . are slightly separated from the palatine processes of the pre-maxillaries " (loc. cit. p. 106), that in the same animal the " anterolateral vomers . . ..have a very temporary and doubtful existence independent of these processes of the premaxillaries " (p. 179), and that while the palatine processes of the premaxillaries of the Shrew in having " no separate antero-lateral vomer attached to them " have "the same deficiency " as the Mole (p. 200), he has both involved himself in a contradiction and shown that he was unable to draw a sharp distinction between the palatine processes of the premaxillse and his anterior paired (or lateral) vomers. The salient conclusions which arise out of Parker's investigation are (a) that we can no longer regard those structures ordinarily described among mammals as "palatine processes of the premaxillae" as throughout homologous ; and (j3) that the latter are, in a number of cases, no parts of the premaxillse at all, but rather referable to the vomerine category. In his discovery of the complex nature of the (non-pathological) premaxilla of mammals Parker is at one with Albrecht, who has shown that there is reason for regarding the premaxillse of the adult Ornithorhynchus as a combination of distinct elements '. All those mammals for which Parker has recorded the presence of " anterior paired vomers " are long-nosed 2. Comparison of the skulls of the adults with those of the young, as figured by him, will show that while the bones in question may iu some cases pass over to the true vomers, they more generally remain exclusively related to Jacobson's organ, which they ensheath in the form of the so-called premaxillary palatine processes, and their products of fusion and metamorphosis lie, for the most part, within the area of the latter as ordinarily described-occupy, that is to say, that of the palatine lobe of Caiman niger (vo.'", fig. 2), in which the present inquiry finds its focus. Putting all together, nothing is clearer than that the vomers aud palatine processes of the premaxillaries, which have been, I take it, sufficiently shown to be serial elements of a common category, lie collectively within the area of the vomers of the lower Amniota on one hand, and of the Crocodilian Caiman niger on the other. Collating these facts with those before recapitulated concerning the non-duplication and fundamental relationships of the vomers in the lower Vertebrata, we may most reasonably conclude that the bones referred to as anterior paired vomers and palatine processes have "become separate by absorption" (most probably 1 Anat. Schriften, Hamburg & Leipzig, Op. 31, 1883. 2 Centetes, Cyclothunts, Erinaceus, Galeopithecus, Manis, Orycteropus, Rhyn-chocyon, Sore.v, Talpa, Tatusia. |