1875.] MR. SORBY ON THE COLOURING OF BIRDS’ EGGS. 351 
1. On the Colouring-matters of the Shells of Birds’ Eggs. 
By H. C. Sorsy, F.R.S., F.L.S., F.Z.S., &c., Pres. 
R.M.S. 
[Received April 30, 1875.] 
TABLE or ConrTenTs. 
Page | Page 
HoirodachOn tasetsessecce settee 351 | The various colours of eggs them- 
Method of study................0068 352 Selvesi!: 0... BR ee 359 
Description of the colouring- Connexion between the colouring- 
TURAL LENA re oiiate ss sina tciavisaieinbaseeite 353 matters of the eggs and the 
Oorhodeine ....................c008 354 structure of the birds ...... 360 
MNOCY AN, tate sscceeSeeecseree te eee 395 | Eggs of the Tinamous............... 360 
Banded oocyan .............00008 355 | Connexion between the colouring- 
Yellow ooxanthine ............... 356 matters of eggs and other or- 
Rufous ooxanthine............... 357 ganic products,,........eseees+ 362 
Substance giving narrow ab- Relations of oorhodeine............ 363 
sorption-bands in the red ... 358 | Relations of the OOcCyaNS ......... 364 
Lichnoxanthine .................. US|" Conclusion .s2-5<cc.2.¢..etassceennes 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 my various pub- 
lished papers, 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 well- 
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 ¢, and that both the redder and greener 
colours are due to bile-pigments ¢ and are perhaps derived from the 
feeces 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 hemoglobin 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 con- 
tamination with substances whose function is altogether different. 
* Proceedings of the Royal Society, 1873, vol. xxi. p, 442. 
+ Leuckart, ‘ Handworterbuch d. Physiologie,’ vol. iv. 894. 
{ Naumannia, 1858, p. 393. 
§ Blasius, Zeitsch. fur wiss. Zoologie, xvii. p. 480. 
