Page:Encyclopædia Britannica, Ninth Edition, v. 18.djvu/58

48 K NITHOLOG Y Blasius, of Prof. Cabanis and of Sundevall. To the present writer the order thus prescribed seems to be almost the very reverse of that which the doctrine of Evolution requires, and, so far from the Turdidte being at the head of the Oscines, they are among its lower members. There is no doubt whatever as to the intimate relationship of the Thrushes (Turdidx) to the Chats (Saxicolinie), for that is not borne admitted by nearly every systematizes Now most author- out by i^gg on classification are agreed in associating with the ces> latter group the Birds of the Australian genus Pctrceca and its allies the so-called " Jlobins " of the English- speaking part of the great southern communities. But it so happens that, from the inferior type of the osteological characters of this very group of Birds, Prof. PARKER has called them (Trans. Zool. Society, v. p. 152) " Struthious Warblers." Now if the Petrceca-group be, as most allow, allied to the Saxicolinse, they must also be allied, only rather more remotely, to the Turdidce, for Thrushes and Chats are inseparable, and therefore this connexion must drag down the Thrushes in the scale. Let it be granted that the more highly-developed Thrushes have got rid of the low " Struthious " features which characterize their Australian relatives, the unbroken series of connecting forms chains them to the inferior position, and of itself disqualifies them from the rank so fallaciously assigned to them. Nor does this consideration stand alone. By submitting the Thrushes and allied groups of Chats and Warblers to other tests we may try still more completely their claim to the position to which they have been advanced. Without attaching too much importance to the system atic value which the characters of the nervous system afford, there can be little doubt that, throughout the Animal Kingdom, where the nervous system is sufficiently developed to produce a brain, the creatures possessing one are considerably superior to those which have none. Con sequently we may reasonably infer that those which are the best furnished with a brain are superior to those which are less well endowed in that respect, and that this infer ence is reasonable is in accordance with the experience of every Physiologist, Comparative Anatomist, and Palaeon tologist, who are agreed that, within limits, the proportion which the brain bears to the spinal marrow in a .vertebrate is a measure of that animal s morphological condition. These preliminaries being beyond contradiction, it is clear that, if we had a series of accurate weights and measure ments of Birds brains, it would go far to help us in deciding many cases of disputed precedency, and especially such a case as we now have under discussion. To the nor by dispraise of Ornithotomists this subject has never been size of properly investigated, and of late years seems to have been wholly neglected. The present writer can only refer to the meagre lists given by TIEDEMANX (Anaf. und Naturyesch. der Voyel, i. pp. 18-22), based for the most part on very ancient observations ; but, so far as those observations go, their result is conclusive, for we find that in the Blackbird, Turdm merula, the proportion which the brain bears to the body is lower than in any of the eight species of Oscines there named, being as 1 is to 67. In the Redbreast, Erithacus rubecula, certainly an ally of the Turdidse, it is as 1 to 32 ; while it is highest in two of the Finches the Goldfinch, Cardudis elegans, and the Canary -bird, Serimis canarius, being in each as 1 to 14. The signification of these numbers needs no comment to be understood. Evidence of another kind may also be adduced in proof that the high place hitherto commonly accorded to the Turdidae, is undeserved. Throughout the Class Aves it is observable that the young when first fledged generally assume a spotted plumage of a peculiar character nearly each of the body-feathers having a light-coloured spot at I train, its tip and this is particularly to be remarked in most 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 which are peculiar to the immature condition of an animal, and are lost in its progress to maturity, are those vhich 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 invari ably 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. 1 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 success fully 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. Xow, applying these principles to the Thrushes, we shall find that without nor by exception, so far as is known, the young have their first cnar - plumage more or less spotted ; and, except in some three a( r tei or four species at most, 2 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 Turdidx. 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 insufficiency 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 without perception that such questions might arise. In treating of what he termed the Order Vagatores, 3 punk of including among others the Family Corvidx 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 him to it. In one of the earlier treatises of Prof. PARKER, he has expressed (Trans. Zool. Society, v. p. 150) his approval of Macgillivray s views, adding that, " as that speaking, singing, mocking animal, Man, is the culmination of the Mammalian series, so that bird in which the gifts of speech, song, and mockery are combined must be considered as the top and crown of the bird-class." Any doubt as to which Bird is here intended is dispelled by another passage, written ten 1 See Darwin, Descent of Man, cliaps. xv., xvi. 2 According to Mr Seebohm (Cat. Birds Brit. Museum, v. p. 232) these are in his nomenclature Merula nigrescens, M. fuscatra, M. gigas, and M. gignntodes. 3 In this Order ho 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 Corvidie and the allied Family we now call Sturnidfe.