770 RECTUM—REDBACK 
(Capito) on the one hand and the Purr-Birps (Monacha) on the 
other. Though the smaller number may be a later and higher 
stage of the tail’s development, it certainly does not confer a higher 
morphological rank on the forms that bear it, as is shewn by the 
fact that the majority of PICARI& have but 5 pairs, and also some of 
the lower PASSERES as Acanthidositia and Xenicus, while it is certain 
that the possession of more than 6 pairs is not an ancestral feature, 
the increase being a comparatively recent acquisition. Indeed the 
number of Rectrices seems to have but little signification, very 
nearly-allied species differing in this respect. Thus of Oreocincla 
(THRUSH) two species have 7 pairs, and all the rest 6. Among the 
CorMORANTS the common Phalacrocorax carbo has 7 pairs and the 
smaller P. graculus (SHAG) 6 pairs. Still greater diversity obtains 
among the SNIPES, the ordinary species of the Old World, Gallinago 
celestis, has 7, that of North America, G. wilsont (otherwise not 
readily distinguished from the former) has 8, as also has G. major, 
while G. gallinula, the Jack Snipe, but 6, though in the last two 
cases accompanied by osteological differences, and the Pin-tailed 
Snipe of Asia, G. stenuwra, sometimes exhibits 14 pairs. Several 
other similar cases are on record and many must exist that have 
not been detected. A difference too may depend upon sex, as 
with the PEACOCK, which has 10 pairs, being one more than the 
Peahen. 
Of the varied forms and functions of the Rectrices there is little 
need to speak. The differences displayed by the first are obvious 
to all who have the least acquaintance with Birds. The forked tail 
of a SWALLOW is proverbial, and the pointed tail of a PARAKEET 
hardly less familiar, while the erect tail of the Cock with its gallant 
streamers affords a striking contrast to the flattened tail of the 
Goose that feeds beside him in the poultry-yard. Similarly as to 
function: in the Peacock, QUEZAL and some other birds the 
rectrices serve but as a support to the showy train that covers and 
hides them: in the WoopPECKERS, TREE-CREEPERS, and many 
forms not allied to either, they are of the greatest importance in 
the bird’s economy, as without their support it would be unable to 
obtain a living ; but many are the cases in which ingenuity is at a 
loss to assign the reason for some remarkable peculiarity offered by 
the Rectrices. 
RECTUM, the portion of the intestine (DIGESTIVE SYSTEM, 
p. 138) between the insertion of the c#CA and the cLoaca. Birds, 
the Latitz and Palamedea excepted, have no colon, and the Rectum 
descending along the right KIDNEY is generally shorter than the 
distance from the upper end of the kidneys to the cloaca. In the 
Ostrich, however, it is of enormous length (p. 140) and width. 
REDBACK, a name applied in North America to the DUNLIN 
