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Show 1875.] MR. SORBY ON THE COLOURING OF BIRDS' EGGS. 351 1. On the Colouring-matters of the Shells of Birds' Eggs. By H. C. SORBY, F.R.S., F.L.S., F.Z.S., &c, Pres. R.M.S. [Received April 30, 1875.] TABLE OP CONTENTS. Page The various colours of eggs themselves 359 Connexion between the colouring-matters of the eggs and the structure of the birds 360 Eggs of the Tinamous 360 Connexion between the colouring-matters of eggs and other organic products 362 Relations of oorhodeine 363 Page Introduction 351 Method of study 352 Description of the colouring-matters 353 Oorhodeine 354 Oocyan 355 Banded oocyan 355 Yellow ooxanthine 356 Rufous ooxanthine 357 Substance giving narrow absorption- bands in the red ... 358 Lichnoxanthine 358 Relations of the oocyans 364 Conclusion 365 INTRODUCTION. Any one examining a large series of different kinds of birds' eggs could not fail to be struck with the almost unlimited variety of their tints, and might readily be led to suppose that nothing definite could be made out from them. I have, however, found, by employing the same kind of spectrum method of inquiry which has led to such definite results in the case of plants, as shown in m y various published paper*?, especially in one on comparative vegetal chromatology*, that all this apparent confusion is due simply to a variation in the relative and total amount of a limited number of definite and welk marked substances. So far as I have been able to ascertain, they have never been investigated by the spectrum method, and little more has been done than to offer such crude suggestions as that the redder colours are due to altered blood, which passes through the swollen vessels of the oviduct f, and that both the redder and greener colours are due to bile-pigments J and are perhaps derived from the faeces in the cloaca §. As I shall show, there is indeed good physical evidence to prove that the characteristic colouring-matters of eggs are closely connected either with haemoglobin or bile-pigments, but not in such a manner as would agree with the above-named rough, almost mechanical theories, which were formed before the application of the spectrum method of inquiry made it possible to identify or distinguish organic colouring-matters of the kind now under consideration. So far as I am able to judge from what is now known, the colouring of eggs is due to definite physiological products, and not to accidental contamination with substances whose function is altogether different. * Proceedings of the Royal Society, 1873, vol. xxi. p. 442. t Leuckart, ' Handworterbuch d. Physiologie,' vol. iv. 894. I Naumannia, 1858, p. 393. § Blasius, Zeitsch. fiir wiss. Zoologie, xvii. p. 480. |
