INTRODUCTION IG 
particularly to be remarked in many groups of Oscines, so much so indeed, 
that a bird thus marked may, in the majority of cases, be set down with- 
out fear of mistake as being immature. All the teachings of morphology 
go to establish the fact that any characters, not specially adaptive, which 
are peculiar to the immature condition of an animal, and are lost in its 
progress to maturity, are those which its less advanced progenitors bore 
while adult, and that in proportion as it gets rid of them it shews its 
superiority over its ancestry. This being the case, it would follow that an 
animal which at no time in its life exhibits such, marks of immaturity or 
inferiority must be of a rank, compared with its allies, superior to those 
which do exhibit these marks. The same may be said of external and 
secondary sexual characters. Those of the female are almost invariably to 
be deemed the survival of ancestral characters, while those peculiar to the 
male are in advance of the older fashion, generally and perhaps always the 
result of sexual selection.! When both sexes agree in appearance it may 
mean one of two things—either that the male has not lifted himself much 
above the condition of his mate, or that, he having raised himself, the 
female has successfully followed his example. In the former alternative, 
as regards Birds, we shall find that neither sex departs very much from the 
coloration of its fellow-species ; in the latter the departure may be very 
considerable. Now, applying these principles to the Thrushes, we shall 
find that without exception, so far as is known, the young have their 
first plumage more or less spotted ; and, except in some three or four 
species at most,” both sexes, if they agree in plumage, do not differ greatly 
from their fellow-species. 
Therefore as regards capacity of brain and coloration of plumage 
priority ought not to be given to the Turdide. It remains for us to see 
if we can find the group which is entitled to that eminence. Among 
Ornithologists of the highest rank there have been few whose opinion is 
more worthy of attention than Macgillivray, a trained anatomist and a 
man of thoroughly independent mind. Through the insufliciency of his 
opportunities, his views on general classification were confessedly imperfect, 
but on certain special points, where the materials were present for him to 
form a judgment, one may generally depend upon it. Such is the case 
here, for his work shews him to have diligently exercised his genius in 
regard to the Birds which we now call Oscines. He belonged to a period 
anterior to that in which questions that have been brought uppermost by 
the doctrine of Evolution existed, and yet he seems not to have been with- 
out perception that such questions might arise. In treating of what he 
termed the Order Vagatores,? including among others the Family Corvide 
—the Crows, he tells us (Brit. Birds, i. pp. 485, 486) that they “are to 
be accounted among the most perfectly organized birds,” justifying the 
opinion by stating the reasons, which are of a very varied kind, that led 
1 See Darwin, Descent of Man, chaps. xv. xvi. 
2 According to Seebohm (Cat. B. Brit. Mus. v. p. 232) these are in his nomencla- 
ture Merula nigrescens, M. fuscatra, M. gigas and M. gigantodes. 
3 In this order he included several groups of Birds which we now know to be but 
slightly if at all allied ; but his intimate acquaintance was derived from the Corvid# 
and the allied Family we now call Sturnidx. 
