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, aud 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 coiuiexiou with tlie 

 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 Trochilidse 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 vibrissse or into a brush, as we saw 

 was the case with the MelijjJiaffince and Nectariniince. Tlie nectar 

 will then ascend to the tubular portion by capillary attraction ; or 

 the brush may be moistened or soaked with nectar hke a sponge, 

 and the nectar may then be sucked up into the tubes. This process 

 finds an analogue iu the proboscis of Bees and Butterflies. 



EXPLANATION OF PLATE XVI. 



s.h, Serpi-hyoid ; m.k, mylo-hyoid ; si.h, stylo-hyoid ; ff.Ji, genio-hyoid ; eg, 

 ceratoglossal ; tr.fi, traeheo-hyoid ; ifr.sif, tracheo-aternalis ; ^r./, tracheo- 

 laryngeus ; tr, trachea ; b.h, basihyal ; it.h, iirohyal. 



Fig. 1. Nectarinia splendida. The mylo-hyoid and serpi-hyoid muscles are 

 removed. 



2. Zostcrops lateralis. Ventral view, after the removal of the mylo- and 



serpi-hyoid. 



3. Nectarinia splendida. Ventral view of the muscles between the mandi- 



bles, 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. Troohiliis, sp. Semidorsal view, to show the geuio- and stylo-hyoid 



muscles curving round the skull. 



6. Prostheinadera. Ventral view, after removal of the mjdo- 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 malaccends. Dorsal view of the right tube of the tongue. 



9. Cinnyris auriceps. Dorsal view of the left tube. 



10. Anthothrejites suhcoUaris. Ventral view of the tubular part of the 

 tongue. 



