OCR Text |
Show 370 PROF. A. H. GARROD ON THE [Apr. 1, cord, which it resembles in consistence. The " mucous " tissue in this case is entirely developed between the external fibrous covering of the windpipe and the middle ring-carrying layer, the rings themselves not varying in the least, as far as I can detect, from their arrangement in the female. Tetrao urogallus (a male, not quite full-sized, and without any trace of the cervical loop developed) differs from the female of T. tetrix only in a few details. All the rings and semirings are thinner, and the interannular intervals greater. The posterior vertical bar is undistinguishable. Anteriorly, however, the lowermost seven tracheal rings are not thinned in the middle line, where they, above the penultimate, articulate above and below to form what becomes almost an anterior vertical bar as well. The corresponding parts of the Fig. 20. Fig. 21. Front view. Tetrao urogallus. Back view. penultimate and last rings, considerably narrower than in T. tetrix, expand and consolidate into an elongate lozenge, with a much shorter one above it, from the lateral angles of which the rings are continued, and from the inferior angle of the lower of which the articulating (and subsequently fusing) surfaces for the anterior ends of the first bronchial rings arise. The second semiring also articulates with the first, as in the allied birds, with, however, a considerably larger interannular interval than in T. tetrix. The lateral parts of the first semiring being markedly convex upwards, at the same time that the incurved last tracheal ring sends downwards rather lengthy processes from its posterior extremities as well as the deep lozenge-shaped cartilage in front, the interval between the two agrees with the section of a plano-concave lens. Some of the bronchial semirings are bifid at their extremities; and the bronehidesmus is very strong. Tetrao cupido is intermediate in its tracheal bifurcation between Lagopus scoticus together with L. mutus, on the one band, and Tetrao |