INTRODUCTION ii? 



particularly to be remarked in many groups of Oscines, so mvicli 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, ajiplying 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 dift'er greatly 

 from their fellow-species. 



Therefore as regards capacity of brain and coloration of plumage 

 priority ought not to be given to the Turdidx. It remains for us to see 

 if we can find the groui^ 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 insufiiciency 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 Corvidas 

 — 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 



•^ See Darwin, Descent of Man, chaps, xv. svi. 



^ According to Seebohm {Cat. B. Brit. Mvs. v. p. 232) these are in his nomencla- 

 ture Merula nigrescens, M. fuscatra, M. gigas and M. gigantodes. 



^ 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 Corvidse 

 and the allied Family we now call Sturnidie. 



