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Show 1894.] YOUNG OE ECHIDNA ACULEATA. 13 referred to here. But though Ornithorhynchus has probably remained closer to the Prototherian stock than Echidna, the presence of a horny bill in both forms as well as the characters to which attention has recently been drawn by Westling1 and Howes2 seem to indicate the close genetic relation of the two genera, in spite of their special adaptive characters. Note (Jan. 8th, 1894).-Since this paper was sent in for publication, I have received from Prof. Wilson and Mr. Martin a copy of their recent paper, " Observations upon the Anatomy of the Muzzle of Ornithorhynchus " (Macleay Memorial Volume, part 6), in which it is stated that " the epidermis of the muzzle of Platypus is no more ' horny' than that of a dog's nose, from the texture of which indeed it does not greatly differ." There is no doubt, however, that in m y specimens of the young of both genera the horny layer of the epidermis covering the muzzle is so thick as to justify one in speaking of a " horny " snout, even though this is of course more flexible than the beak of a Turtle or Bird : and in these specimens there can have been no possibility of a partial desiccation. I should also mention that " the peculiar rod-like tactile organs in the integument and mucous membrane of the muzzle of Ornithorhynchus.," previously described by Poulton, have beeu treated of by the same authors in part 7 of the' Macleay Memorial Volume,' in which it is stated that no such organs are present on the anterior portion of the snout and palate of Echidna: this agrees with m y own observations. EXPLANATION OF THE PLATES. PLATE I. Fig. 1. Ventral view of a young Echidna aculedta, 125 cm. in length along the dorsal curve (Stage I.). 2. Ventral view of an older (male) specimen, 2 P 5 cm. in length (Stage II.). 3. The snout in longitudinal section (Stage II.), the cut having been made to the left side of the septum nasi, so as to show the left nasal chamber. The greater part of the glandular ridge on the septum has been removed, the anterior part, enclosing Jacobson's organ, being left in situ. P L A T E II. Figs. 4-11 represent transverse sections through the snout of Stage I. Fig. 4. Through the external nostril and caruncle. 5. Through the " ali-nasal turbinal," just in front of Jacobson's organ. 6. Through the naso-palatine and Jacobson's ducts. 7. Through about the middle of Jacobson's organ. 8. Through the posterior end of Jacobson's organ. 9. Rather farther back than fig. 8, showing the end of Jacobson's cartilage. 10. Through the septal gland and maxillo-turbinal. 11. Through the septal gland, maxillo-turbinal, and ethmo-turbinal. 12. Section through the integument and a sweat-gland of the lower jaw (Stage II.). 1 Bihang till K. Svenska Yet.-Akad. Handl. (Stockholm), Bd. xv. 1890. 2 " O n the Mammalian Pelvis, with special reference to the young of Ornithorhynchus anatinus," Journ. Anat. and Physiol, vol. xxvii. (1893). |
