148 PTERYLOGEAPHY. 



neck-space nearly to the middle of the neck. At the same time the outer branch of the inferior 

 tract (PL X, fig. 7) is smaller and weaker, and, like the hinder part of the dorsal tract, more sparsely 

 feathered. In the wing there are twenty-nine remiges in A. cinereus, canademis, cygnoides, 

 albifrons, and leucopsis, and thirty in A. torquatus; in the tail I find fourteen feathers in 

 A. torquatus and pollicaris, sixteen in most species, and exceptionally seventeen, but eighteen only 

 in A. canadensis. A. gerrlda, an East Indian species, very similar to A. madagascariensis, has 

 twelve rectrices and twenty-five remiges. 



4. Mcrgns. This genus, from the absence of the lateral neck-space and the shortness of 

 the spinal space, approaches most closely to the Pochards ; but the spinal space rises higher upon 

 the neck, even reaching to its middle. M. merganser, serrator, and cuciillatus, have eighteen 

 rectrices ; M. albettus possesses only sixteen ; but all four have the same number of remiges, 

 namely, twenty-seven. 



Lastly, I have to notice the nestling plumage in this family, and to state with regard to 

 the Domestic Goose, in which I carefully examined it, that the down-feathers of which it consists 

 are true feathers, provided with shafts and tubes, which, however, are probably seated upon the 

 points of the future contour-feathers, just as we have seen them to be among the Cursorial Birds 

 (p. 119). The shaft and barbs of these down-feathers are rigid and of a yellow colour, and ter- 

 minate in fine capillary tips. The barbules attached to the lower part of the barbs are likewise 

 thin, filamentous, or capillary, but have a short, laminar basal piece, although no trace of knots 

 or hooks. The barbs stand very far apart on the shaft, and are, therefore, not numerous. 



4. STEGANOPODES. 



This family, like the preceding, has a very persistent type of pterylosis, and presents no 

 generic differences, except, perhaps, a variation in the density of the plumage, which appears to 

 be dependent on the climates in which the birds live, and is much more considerable in northern 

 than in tropical genera. The latter, such as Phaeton, Tachypetes, and Ilalieus, have certainly no 

 aftershaft on the contour-feathers ; but even in the other genera I have not met with it, and 

 it is therefore probably generally wanting. With regard to the feathers and tracts, the Stegano- 

 podes are, however, clearly enough distinguished from the Unguirostres. The feathers are here 

 always smaller, more pointed, and far less curved than in the Ducks and Geese. Nevertheless, 

 they are not placed closer together, but, on the whole, are rather wider apart and more sparse. In 

 the tracts the chief difference presented is the complete absence of a pectoral branch on the inferior 

 tract, the latter gradually becoming narrower from the commencement of the breast, and passing, 

 without the least break, from the pectoral surface to the ventral. Connected with this is an 

 abbreviation of the very narrow inferior space, for this never passes forward beyond the point of 

 furcation of the furcula, although posteriorly it attains the anus. The lateral space of the trunk 

 is broader, at least in Dysporus, where it is continued between the lumbar and dorsal tracts, and 

 reaches the true tail, which is the case in no other genus. To make up for this, Dysporus has 

 quite a short spinal space on the interscapulium ; but the axillary tracts are connected with the 

 sparse lateral portions of the dorsal tract. This occurs in a still higher degree in all the other genera, 



