-984 TRACHEA 



•excepted, a single ampulla often of considerable size being thrown 

 ■out on one side — usually the left. This structure obtains ap- 

 parently throughout all the " Freshwater Ducks " or Anaiinse, as 

 well as in Somateria and Tachyeres, but it is subject to great 

 exaggeration and, though occasionally absent as in CEdemia, becomes 

 very complicated in the group of "Diving Ducks," forming 

 in many cases a tympanum, whose bony walls are fenestrated and 

 the spaces filled with a resonant membrane,^ while it attains its 

 greatest magnitude in the Merginse. Tadorna has two bony ampullse, 

 one on each side, and dilatations are also present in Chenalopez, 

 Sarcidiornis and, according to Eyton (op. cif. p. 83, pi. i. figs. 1, 2), 

 in Chloephaga magellanica. In Dendrocygna the labyrinth is com- 

 posed of two oblong chambers, and takes the form of a symmetrical 

 shield-shaped box {Ibis, 1859, p. 366). 



Quite as remarkable is the lengthening of the Trachea in some 

 birds during adolescence, so that to be contained conveniently it is 

 looped, and this formation is frequentlj'', though not always, con- 

 fined to one or the other sex. In the male of Tetrao urogallus 

 (Capercally) and in the female of Anseranas there is a simple 

 subcutaneous loop. In the female of the Old -World Painted 

 Snipes (p. 887), Rostrahda, the loop extends ventrally over the 

 furcula, and more or less over the pectoral muscles {cf. Wood- 

 Mason, Proc. Zool. Soc. 1878, p. 745), and a similar arrangement is 

 found in the males of most Cracinse (Curassow), while it occurs in 

 both sexes of Penelope jacucaca, though most of the Penelopinse 

 (Guan) have no loop at all. Among Passeres a series of coils is 

 found in both sexes of Phonygama, and in the males of Manucodia 

 (Manucode). In the male of Anseranas the convolutions of the 

 Trachea lying outside the pectoral muscles are not only subject 

 to variation in number, but they may be placed on either side of 

 the body {cf. Yarrell, Trans. Linn. Soc. xv. pp. 383, 384, pis. 

 xiii. xiv.), the form of the coracoid on that side being modified 

 accordinglj'-. A curious peculiarity is exhibited by the Crested 

 Guinea Fowls {suprh, p. 401), in both sexes of which the 

 symphysis of the furcula is dilated so as to lodge a short tracheal 

 loop {torn. cit. pi. ix.). 



The furcula and coracoids are not, however, the only bones 

 which are modified by the excessive lengthening of the Trachea. 

 As has long been known, some of the Swans and Cranes have 

 their sternum invaded by it ; but each in a different way — the 



^ Very remarkable is the tracheal structure of Harelda and Rhodoiussa, but 

 want of space renders it impossible to particularize all the peculiarities in this 

 group of Anatidas. Reference may be made to the classical papers of Latham and 

 Yarrell (Trans. Linn. Soc. iv. pp. 90-128, and xv. pp. 378-388), as Avell as to 

 Eyton's Monograph above cited, and the observations of Garrod {Proc. Zool. Soc. 

 1875, pp. 1.51-156) and Forbes {op. cit. 1882, pp. 347-353). 



