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Show 1883.] APPARATUS OF THE TENUIROSTRES. 69 mouth-cavity. The mouth is thus wholly filled up. Through the contraction of the genio-hyoid muscles the tongue will be protruded from the mouth. Now, if the serpi-hyoid and mylo-hyoid muscles relax, and the tracheo-laryngeus and tracheo-hyoideus, on the other hand, by their contraction depress the larynx and at the same time depress the posterior part of the tongue, a vacuum will be produced between tongue and palate. This space, again, is in connexion with the tubes of the tongue, and therefore will be filled by the fluid into which the tips of these tubes may be inserted. In the birds in question the fluid is honey or nectar. Consequently sucking is accomplished automatically through the mere protrusion of the tongue. It is clear that this process is very simple in the Trochilida? with their complete tubes ; but they will not be able to suck if there is not fluid enough to fill the whole of the anterior opening of the tubes, since air would rush in instead of nectar. This eventual inconvenience seems to me to be prevented or overcome by the anterior portion of the tubes being broken up into vibrissa? or into a brush, as we saw was the case with the Meliphayinas and Nectariniina. The nectar will then ascend to the tubular portion by capillary attraction ; or the brush may be moistened or soaked with nectar like a sponge, aud the nectar may then be sucked up into the tubes. This process finds an analogue in the proboscis of Bees and Butterflies. EXPLANATION OF PLATE XVI. s.h, Serpi-hyoid; m.h, mylo-hyoid; st.h, stylo-hyoid; g.h, genio-hyoid; ceratoglossal; tr.h, tracheo-hyoid; tr.st, tracheo-sternalis; tr.l, tracheo-laryngeus ; tr, trachea ; b.h, basihyal; u.h, urohyal. Fig. 1. Nectarinia splendida. The mylo-hyoid and serpi-hyoid muscles are removed. 2. Zosterops lateralis. Ventral view, after the removal of the mylo- and serpi-hyoid. 3. Nectarinia splendida. Ventral view of the muscles between the mandibles, after removal of the skin. 4. Nectarinia splendida. The same as in fig. 3, after removal of the serpi-and genio-hyoids, to show the connexion of the mylo-hyoid with the soft transversely folded part of the tongue's sheath. 5. Trochilus, ep. Semidorsal view, to show the genio- and stylo-hyoid muscles curving round the skull. 6. Prosthemadera. Ventral view, after removal of the mylo- and serpi-hyoid. 7. The same as in fig. 6; but the whole apparatus of the tongue is bent backwards and downwards to show the anterior end of the larynx. 8. Anthothreptes malaccensis. Dorsal view of the right tube of the tongue. 9. Cinnyris auriceps. Dorsal view of the left tube. 10. Anthothreptes subcollaris. Ventral view of the tubular part of the tongue. |