Page:Encyclopædia Britannica, Ninth Edition, v. 18.djvu/99

O W L arrangement of the Owls which he then proposed ; and it was hardly until the publication ten years later of Nitzsch s Pterylographie that rational grounds on which to base a division of the Owls were adduced. It then became manifest that two very distinct types of pterylosis existed in the group, and further it appeared that certain differ ences, already partly shewn by Berthold (lieitr. zur Anatomie, pp. 166, 167), of sternal structure coincided with the pterylological distinctions. By degrees other significant differences were pointed out, till, as summed up by Prof. Alphonse Milne-Edwards (Ois. foss. de la France, ii. pp. 474-492), there could no longer be any doubt that the bird known in England as the Screech-Owl or Barn-Owl, with its allies, formed a section which should be most justifiably separated from all the others of the group then known. Space is here wanting to state particularly the pterylological distinctions which will be found described at length in Nitzsch s classical work (English translation, pp. 70, 71), and even the chief osteo- logical distinctions must be only briefly mentioned. These consist in the Screech-Owl section wanting any manubrial process in front of the sternum, which has its broad keel joined to the clavicles united as a furcula, while posteriorly it presents an unbroken outline. In the other section, of which the bird known in England as the Tawny or Brown Owl is the type, there is a manubrial process; the furcula, far from being joined to the keel of the sternum, often consists but of two stylets which do not even meet one another; and the posterior margin of the sternum pre sents two pairs of projections, one pair on each side, with corresponding fissures between them. Furthermore the Owls of the same section shew another peculiarity in the bone usually called the tarsus. This is a bony ring or loop bridging the channel in which lies the common extensor tendon of the toes which does not appear in the Screech-Owl section any more than in the majority of birds. The subsequent examination by M. Milne-Edwards (Souv. Arch, du Museum, ser. 2, i. pp. 185-200) of the skeleton of an Owl known as Fhodilus (more correctly Photodilus) badius, hitherto attached to the Screech-Owl section, shews that, though in most of its osteological characters it must be referred to the Tawny Owl section, in several of the particulars mentioned above it resembles the Screech-Owls, and therefore we are bound to deem it a connecting link between them. The pterylological characters of Photodilus seem not to have been investigated, but it is found to want the singular bony tarsal loop, as well as the manubrial process, while its clavicles are not united into a furcula and do not meet the keel, and the posterior margin of the sternum has processes and fissures like those of the Tawny Owl section. Photodilus having thus to be removed from the Screech-Owl section, Prof. Milne-Edwards has been able to replace it by a new form JIdiod dus from Madagascar, described at length by him in M. Grandidier s great work on the natural history of that island (Oiseaux, i. pp. 113-118). The unexpected results thus obtained preach caution in regard to the classification of other Owls, and add to the misgivings that every honest ornithologist must feel as to former attempts to methodize the whole group misgivings that had already arisen from the great diversity of opinion displayed by previous classifiers, no two of whom seem able to agree. Moreover, the difficulties which beset the study of the Owls are not limited to their respective relations, but extend to their scientific terminology, which lias long been in a state so bewildering that nothing but the strictest adherence to the very letter of the laws of nomenclature, which are approved in principle by all but an insignificant number of naturalists, can clear up the confusion into which the matter has been thrown by heed less or ignorant writers some of those who are in general most careful to avoid error being not wholly free from blame in this respect. A few words are therefore here needed on this most unprofitable subject. 1 Under the generic term Strix Linnaeus placed all the Owls known to him ; but Brisson most justifiably divided that genus, and in so doing fixed upon the S. stridula the aforesaid Tawny Owl as its type, while under the name of Asia he established a second genus, of which his contemporary s S. otus, afterwards to be mentioned, is the type. Some years later Savigny, who had very peculiar notions on nomenclature, disregard ing the act of Brisson, chose to regard the Linnsean 8. flammea the Screech-Owl before spoken of as the type of the genus Strix, which genus he further dissevered, and his example was largely followed until Fleming gave to the Screech-Owl the generic name of Aluco, 2 by which it had been known for more than three hundred years, and reserved Strix for the Tawny Owl. He thus anticipated Nitzsch, whose editor was probably unacquainted with this fact when he allowed the name Hyhris to be conferred on the Screech-Owl. No doubt inconvenience is caused by changing any general practice ; but, as will have been seen, the practice was not universal, and such inconveni ence as may arise is not chargeable on those who abide by the law, as it is intended in this article to do. The reader is therefore warned that the word Strix will be here used in what is believed to be the legitimate way, for the genus containing the Strix stridula of Linnaeus, while Aluco is retained for that including the S. flammea of the same naturalist. Except the two main divisions already mentioned, any further arrangement of the Owls must at present be deemed tentative, for the ordinary external characters, to which most systematists trust, are useless if not mislead ing. 3 Several systematizers have tried to draw characters from the orifice of the ear, and the parts about it ; but | hitherto these have not been sufficiently studied to make the attempts very successful. If it be true that the predomin ant organ in any group of animals furnishes for that group the best distinctive characters, we may have some hope of future attempts in this direction, 4 for we know that few birds have the sense of hearing so highly developed as the Owls, and also that the external ear varies considerably in form in several of the genera which have been examined. Thus in Surnia, the Hawk-Owl, and in Nyctea, the Snowy Owl, the external ear is simple in form, and, though pro portionally larger than in most birds, it possesses no very remarkable peculiarities, a fact which may be correlated with the diurnal habits of these Owls natives of the far north, where the summer is a season of constant daylight, and to effect the capture of prey the eyes are perhaps more employed than the ears. 5 In Bubo, the Eagle-Owl, though 1 It has been dealt with at greater length in The Ibis for 1876 (pp. 94-105). 2 The word seems to have been the invention of Gaza, the trans lator of Aristotle, in 1503, and is the Latinized form of the Italian A llocco. 3 It is very much to be regretted that a very interesting form of Owl, Sceloglaux albifacies, peculiar to New Zealand, should be rapidly becoming extinct, without any effort, so far as is known, being made to ascertain its affinities. It would seem to belong to the Strigine section, and is remarkable for its very massive clavicles, that unite by a kind of false joint, which in some examples may possibly be wholly ancylosed, in the median line. 4 This hope is strengthened by the very praiseworthy essay on the Owls of Norway by Herr Collett in the Forhandlinger of Ohristiania for 1881. 5 But this hypothesis must not be too strongly urged; for in Carine, a more southern form of nocturnal (or at least crepuscular) habits, the external ear is perhaps even more normal. Of course by the ear the real organ of hearing is here meant, not the tuft ol feathers often so called in speaking of Owls. XVIIT. 12