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Show 358 MR. H. c SORBY ON THE [May 4, of the eggs of the rufous Tinamou-and not to green, like that of the fresh eggs of the E m u. 6. Substance giving narrow absorption-bands in the red.-Unfortunately I have not yet succeeded in obtaining this in sufficient quantity, or sufficiently free from other substances, to be able to decide whether its true colour is blue, green, or brown; but the fact of its giving a spectrum with several narrow absorption-bands in the red would certainly indicate that, when mixed with other colouring-matters, it would cause them to have an abnormally browner tint. Small quantities of it occur in very many eggs ; but I have not yet found it so abundant in any as to exercise a more important effect on the general colour than to make it somewhat more dull. Since the entire spectrum is not accurately known, I will merely give the position of the different very narrow absorption-bands in millionths of millimetres of wave-length. The most complete spectrum shows three bands. On adding excess of ammonia, that nearest the red end alone remains, whilst the addition of a small excess of a strong acid removes all but the central band-and when the excess is considerable, raises this band towards the blue end. These facts will be better shown by the following table :- Centre of bands. Most complete spectrum 668 648 628 With excess of ammonia 668 With a little acid 613 With much acid 641 By means of these bands a very small quantity of this substance can easily be recognized, lt is not readily decomposed-but, when acted upon with oxidizing reagents, may be changed into another colouring-matter, giving rise to a spectrum with one or two somewhat obscure bands. 7. Lichnoxanthine.-In my paper on comparative vegetal chro-matology *, I have described a substance which occurs in greater or less amount in almost all classes of plants, from the lowest to the highest, but is more especially abundant in, and characteristic of, lichens and fungi, and for this reason has been named by m e lichnoxanthine. The spectrum shows strong general absorption of the blue end down to about wave-length 510 millionths of a millimetre, and a much weaker general absorption down to about 590 millionths. Acids and alkalis produce very little change; and it is very slowly altered by strong oxidizing reagents. I have been able to prepare it artificially by the decomposition of resins. Some such substance is undoubtedly present in small quantity in very many kinds of birds' eggs; and occasionally there is so much as to materially modify the general colour. It may occasionally have been, to some extent, derived from the decayed vegetable matter of the nest, or, in the case of eggs which have been kept long, may be partly due to the growth of minute fungi; but, at the same time, a very closely allied, * Proc. Roy. Soc. 1873, vol. xxi. p. 462. |
