rcb. 3. 1887] 



NA TURE 



ZIZ 



Thus, by the end of the tenth day, the reptilian type or fore 

 foot has lieen attained, anfl the amphil>ian type lost, whilst the 

 limb as a whole is now a fore-leg no longer, but a wing, 

 thoroughly specialised by evolutional transformation. 



The fore-limb has not simply become modified into a wing by 

 the shortening of the pollex and third ray, the enlargement of 

 the second, and the abortion of the fourth and fifth of a fore- 

 paw, like that of the lizard ; but we have now the historical 

 representatives of three more rays which have cropped up since 

 the end of the eighth day. 



I have repeatedly noticed that aborted parts, like over- 

 shadowed plants, are late to appear, and soon wither, or are 

 arrested in their growth. This is the case here, for the 

 new rays are late, small, and scarcely functional in the 

 fullest development. They are not lost, however, but, like 

 certain larval structures to be found in the skulls of the 

 highest types of birds, they are built up into the finished wing, 

 although they form an unimportant part of it as far as function 

 goes. 



The first of these additional rays is the "pre-poUex " ; this is a 

 lunate tract of fibro-cartilage attached to the inner face of the 

 first metacarpal. The other two are composed of true hyaline 

 cartilage, and appear, one on the ulnar side of the second, 

 and the other on the ulnar side of the third developed 

 metacarp.al- 



I have described them as intercalary metacarpals, for they 

 seem to be the starved twins of the second and third large rays ; 

 each distal carpal, very probably, in the archaic forms carried 

 two rays. Thus there is supposed, for such a fore-limb, a digit 

 inside the pollex of the modern bird, and then two pairs of rays, 

 of which only the inner in each case has been retained. 



The paddle of Ichthyosaurus shows this kind of primitive 

 cheiropterygium admirably. 



Thus we can account for seven carpals and six digits in the 

 wing of the modern bird ; in the legs the specialisation is not so 

 intense, but is very great ; the study of the embryonic stages 

 shows in it many parts that the adult bird gives no signs of 

 whatever. 



Instead of there being even two tarsals, free and functional, 

 there is only one, and that has merely the function of a " sesa- 

 moid," and has been mistaken continually for a bone of that sort, 

 that nucleus answers to our naviculare, morphologically termed 

 the "centrale." 



Notwithstanding the extreme diversity in the habits of existing 

 birds and the great dilTerence seen in their shank bone, this part 

 is always single, although compo.sed of three metatarsals. As 

 in reptiles, the j^int at this part is not between the astragalus 

 and tibia, as in mammals, but through the tarsal series ; no sign 

 of this structure is seen in the adult bird. That which appears 

 to he the condyloid end of the tibia is a row of tarsal bones, the 

 tibiale, fibulare, and intermedium : these have long been known 

 as separate bones in young birds, but their distinctness in 

 the early embryo ;is cartilaginous nuclei has only lately been 

 made out. 



I have been able, however, to demonstrate this repeatedly in 

 diflerent kinds of birds. The centrale also, although seen in the 

 embryo as one of the tarsal series, was not properly identified ; 

 it is a constant element, but becomes degraded. 



The distal series of tarsals exis's as a single tract of cartilage, 

 and then as a single plate of bone. But it is related to three 

 metatarsals, and the middle or thick part is the first to chondrify 

 in the embryo, and to ossify in the chicken or young bird ; there 

 are here three connate nuclei, with very slight signs of distinct- 

 ness. The whole mass answers to our midiUe and external 

 " cuneiform bones," and to the inner half of the " os magnum." 

 Thus five tarsals can be always made out clearly, and two more 

 accounted for. 



The fir-t metatarsal, which has been known, for some time, 

 through the valuable researches of Morse, to have occasionally a 

 proximal as well as a distal rudiment, has, I find, always a 

 proximal ni<liment as well. 



Then, as Dr. G. Baur and -Miss A. Johnson have shown, there 

 is a fifth metatarsal ; it is a small pisiform cartilage, which so )u 

 coalesces with the fourth, and with the great distal tarsal. I can 

 only find a " prehallux" by turning to teratology, and this is 

 not the lawful method. 



There may, however, be some " reversion "or " atavism " in 

 the polydactyle foot of the Dorking fowl, which has a well- 

 developed " pre-halhix " and a double "hallux"; the twin 

 digits of that part have a very ichthyosaurian appearance. 



SCIENTIFIC SERIALS 



AiiiiaU-n dcr Physik 7iitd Chcmic, xxix.. No. II. — B. Dessau, 

 on metal films arising from the disniption of a kathode. Dis- 

 cusses the production of mirror-like films such as obtained by 

 Pliicker, Crookes, and Wright from the disgregation of the 

 metal kathode in Geissler-tubes. With a pointed kathode and 

 a flat glass surface as recipient, the film forms a flat conical 

 deposit, showing interference-rings in reflected light, and proving 

 also the presence of optical dispersive power in the metal. The 

 dispersion in films of platinum, iron, nickel, and silver. It is 

 anomalous in the case of gold and copper. The films are 

 double-refracting, and, in the case of oxidisable metals, dis- 

 appear on oxidation. — Ed. Hagenbach, propagation of electricity 

 in telegraph-wires. Experiments made with chronographic ap- 

 paratus on Swiss lines, together with a discussion of the results 

 of Wheatstone, Walker, Guillemin, and others. Arguing from 

 theory, the author compares, not the apparent speed, but the 

 ratio of the time to the square of the length of circuit. — B. von 

 Kolenko, reply concerning the pyro-electricity of quartz. Main- 

 tains, against Prof. Hankel, that the poles of a warmed quartz 

 crj-stal are not altered during cooling by passing through a flame. 

 — E. Edlund, remarks on H. Hoppe's communication on the 

 theory of unipolar induction. — S. von Wroblewski, on the re- 

 presentation of the rotation between the gaseous and liquid 

 states of matter by isopyknal lines. The transition of state is 

 represented by curves drawn on a diagram having, for given 

 definite densities, pressures as ordinates and temperatures as 

 abscissje ; such curves being termed isopykns or isopyknal lines. 

 The result of examination of these curves shows that, though 

 there is no such thing as an absolutely definite critical tem- 

 perature or critical pressure per sc, there is a critical density for 

 every liquid. — K. Schmidt, on reflection at the surface of crys 

 talline elliptically-polarising media. Experiments made with a 

 crystal of cinnabar, and results compared with the formulze of 

 Voigt and that of Ketteler. The latter leads to closer corre- 

 spondence than the former with the facts of observation. — H. 

 Muraoka, on the deformation of metal plates by grinding. The 

 radius of the curvature produced by grinding metal disks set in 

 a bed of fusible alloy is proportional to the cube of their 

 thickness — K. Exner, validity of lens formulas for non-homo- 

 geneous lenses. — E. Budde, a means of deciding between the 

 electro-dynamic point-lav/s of Weber, Riemann, and Clausius. 

 This gives the elementary theory of an experiment not yet 

 made. — ^J. KoUert, on a new galvanometer. This is practically 

 identical with Gray's form. 



No. 12, 1S86. — C. Fromme, on the galvanic polarisation 

 evoked by small electromotive forces. This gives a first series 

 of results with platinum electrodes in dilute sulphuric acid. — 

 Edm. Hoppe, on the theory of unipolar induction ; with a reply 

 to Prof. Edlund. — F. Himstedt, on a determination of the 

 quantity " v." The method was that of comparison of the two 

 capacities of a condenser ; the result v = 3'0074 X 10'" cm./sec. 

 — R. Lamprecht, on the action of the magnet upon electric dis- 

 charges in rarefied gases, concludes that the law of Biot and 

 Savart holds good as the calculated trajectories agree with 

 cun-es observed by Hittorf in 1869. — A. Foeppl, the spread of 

 the electric charge in conductors. — L. Boltzmann, remarks on 

 the opinion of Ilerr Lorberg on a point in electro-dynamics. — 

 W. Voigt, on the torsion of a rectangular prism of homogeneous 

 ciystalline substance ; a mathematical investigation. — J. Kiewiet, 

 on the elasticity of bending of pure zinc, copper, tin, and their 

 alloys. The moduli of elasticity of alloys is not constant, but 

 depends on the mode of preparation of the alloy as well as on 

 its composition. Wertheim's rule for calculating the moduli of 

 alloys from those of their components, according simply to the 

 proportion of the constituents, appears to be inexact. The 

 change of moduli of alloys with temperature is a simple linear 

 function. — ]. Stefan, on the relation between the theories of 

 capillarity and evaporation. — A. Heritsch, on radiophony. The 

 author combats Graham Bell's view that the condensed gases of 

 a smoke deposit or carbon strip have something to do with its 

 radiophonic properties. He finds that a coke plate heated to 

 redness and then instantly placed in a tube and exposed to inter- 

 mittent illumination from sunlight or electric light, emits tones. 

 He further constructed a sort of flat glow-lamp, which, even 

 when raised to brilliant incandescence, emitted tones when ex- 

 posed to intermittent sunlight. No other source than sunlight 

 was sufficient for this experiment. — G. Kobb, on the spectrum of 

 germanium. — Greiner and Friedrichs, on a new mercury air- 



