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Show 17G DOMESTIC PIGEONS. CHAP. v. of comparison the length from the base of the .beak to the oil-g1a nlc ;and bY this standard ' out of twenty-slx of lthde sa· me birds which had been thus measured, twenty-one 1a wmgs too lonrr, and only five bad them too short. In the tw.enty-one birds the winrrs exceeded in length those of ~he rock-pln·eon, on an avem. ge, bby 12a.. inch '. whilst in the five b1rds they w• erel l1e ss m· 1e ngt·h by on1 y . ou of an inch . . As I was much surpf·n ec. t 1la t t 11 e w·m gs of c1 o . ·ely confined bncls shoulcl thus RO re.q uen. t. y have been increased in length, it occurred to m that It m1gl~t be solely due to the greater length o~ the ~ing-feath~rs; for tins certainly is the case with the jacobm, wluch has wmgs of unusual length. As in almost every cas? I ha~ measured tho folded. winas I subtracted the length of tlns termmal part from that of the ~~paneled wings, and thus I obtained, with a moderato degree of accuracy, the length of the wing from the ends of the two radii answering from wrist to wrist in our arms. ~rho wingR, thus' measured in the same twenty-five birds, now gave a widely different result; for they were proportionally with those of the rock-pigeon too short in seventeen birds, and in only eight t~o long. Of these eight birds, fiv~ were long-beakecl,39 and tins fact perhaps indicates that there is some correlation between the length of the beak and the length of the bones of the wings, in the same manner as with the feet and tarsi. rl'he shortening of the humerus and radius in tho seventeen birds may probably be attributed to disuse, as in the case of the scapulro and furcula to which the wing-bones are attached ;-the lengthening of the wing-feathers, and consequently the expansion of the wings from tip to tip, being, on tho other hand, as completely independent of use and disuse as is the growth of the hair or· wool on our long-haired clogs or long-woolled sheep. To sum up : we may confidently admit that tho length of the sternum, and frequently tho prominence of its crest, tho length of the scapulm and fnrcula, have all been reduced in size in comparison with the same parts in the rock-pigeon. And I 39 it perhaps deserves notice that beaid s thes five birds two of tho eight were barbs, which, as I havo shown, must bo classed in tho same group with tho long-bonked carriers and runts. llnrbs may properly be oalleu short-beaked caniors. It' would, thoroforo, appear ns if, during tuo reduction of their beaks, theu· wings hnd retained a little of that excess of length which is characteristic of thou· nearest relations . and progenitors. CHAP. v. SUMMARY OF DIFFERENCES. 177 presume that this may be safely attributed to disuse or lessen~~ exercise. The wings, as measured from the ends of the radu, have likewise been generally reduced in length; but, owing to the increased growth of the wing-feathers, the wings, from tip to tip, are commonly longer than in the rock-pigeon. The feet, as well as the tarsi conjointly with the middle toe, have likewise in most cases become !'educed; and this it is probable has been caused by theil' lessened use ; bnt the existence of some sort of correlation between the feet and beak is shown more plainly than the effects of disuse. We -have also some faint indication of a similar corrol~tion between the main bones of the wing and the beak. Bumrnary on the Points of Difference between the several Domestic Races, and between the ind-ividual Bi1·ds.-The beak, together with the bones of the face, differ remarkably in length, breadth, shape, and curvature. The skull differs in shape, and greatly in the angle formed by the union of the premaxillary, nasal, and maxillo-jugal bones. The curvature of the lower jaw and the reflexion of its upper margin, as vvell as the gape of the mouth, differ in a highly remarkable manner. rl'he tongue varies much in length, both independently and in correlation with the length of the beak. The development of tho naked, wattled skin over tho nostrils and Tound the ey~s varies in an extreme degree. Tho oy lids and the external orifices of the nostrils vary in length, and are to a certain extent conelatecl with the degree of development of the wattle. The size and form of the cesophagus and crop, and their capacity for inflation, differ immensely. The length of the Heck varies. With tho varying shape of the body, tho breadth and number of the ribs, the presence of processes, the number of the sacral vertebrm, and the length of the sternum, all vary. 1'he number and size of the coccygeal vertebrre vary, apparently in correlation with the increased size of the tail. rl'he size and shape of the perforations in the sternum, and the size and divergence of the arms of the furcula, differ. 1'he oil-gland varies in development, and is sometimes quite aborted. The direction and length of certain feathers have been much modified, as in the hood of the J acobin and the frill of the Turbit. The wing and tail feathers generally vary in VOL. I. N |