| OCR Text |
Show 1887.] IN THE LARYNX OF THE ANUROUS AMPHIBIA. 501 If the apparatus he held to be of none but physiological significance, the clue to its meaning has yet to be found ; it is clearly in no way associated with the development of the vocal sac, nor is it confined to the males, as might be supposed. In the higher forms, however, it is vestigial and of little or no functional importance; and there is nothing forthcoming in any one specimen which is not represented in the male of Chiroleptes. These facts, in view of the uniformity of development of the parts in the latter, would seem to me to suggest that the apparatus has an important morphological significance, and that in the admittedly lowly Australian type the primitive condition is most nearly exemplified. The problem is an interesting one, and further investigation is necessary for its solution. Turning, finally, to the question of general morphological importance, it is clear that the discovery of the epiglottis in the Amphibia, in the form and under the conditions here recorded, carries back a stage further the initiation of one more structure peculiarly characteristic of Mammals. The interest of this is increased when we reflect upon the identity of the Amphibian epiglottis, which is clearly bilaterally symmetrical, if not actually paired, with the initial phase in development of that organ in the human subject as observed by His. The facts show that the origin of this typically M a m m a lian structure must be sought in animals lower than the living Lizards *. It would be wide of the mark to form data for discussing the question of Mammalian affinities upon it. In view, however, of the anticipation of the caecum coli in the Common Frog2, and of the excursions made by those Amphibia with suppressed larval metamorphoses3, in which it is highly probable there may have been foreshadowed the fcetal membranes of the Amniota (cf. Huxley, P. Z. S. 1880, p. 660), the facts here recorded can best be regarded as indicative of similar excursions towards the elaboration of the voice-organ, anticipatory, as has been shown, of the characteristically Mammalian condition. 1 It is of interest here to note the existence of an epiglottis-like fibro-carti-laginous plate in Protopterus. Attention was first drawn to it by Henle {I. c. pp. 5, 6), and it was shortly afterwards described in full and figured by Bischoff (" Descr. Anat. du Lepidosiren paradoxa," Ann. Sci. Nat. t. xiv. Zool. 1840 p. 136). Wiedersheim has refignred it (' Lehrbuch') and recorded (ibid.) the discovery of an analogous structure in Lepidosteus. 2 Huxley, in Huxley and Martin's Elem. Biology, 1875, p. 166. s Especially Nototrema, Weinland, Archiv f. Anat. und Phys. 1854; Hylodes, Peters andGundlach, Monatsb. Berlin. Acad. 1876; Eanaopisthodon, Boulenger, T. Z. S. vol. xii. 1886; Phyllomedusa, v. Ihering and Boulenger, Ann. & Mag. Nat. Hist. vol. xvii. 1886. For a resume of the subject generally, with full references and list of species, see Boulenger on Phyllomedusa, op. cit. p. 464. Cf. also Smith and Cope on Dendrobates, Amer. Naturalist, 1887, pp. 307-311. |
