EGGS 187 
The composition of this pigment long excited much curiosity, 
and it was commonly and rather crudely ascribed to secretions of 
the blood or bile, but unexpected light was shed upon the subject 
by the researches of Mr. Sorby (Proc. Zool. Soc. 1875, pp. 351-365), 
who, using the method of spectrum-analysis, ascertained the exist- 
ence of seven well-marked substances in the colouring-matter of 
eggs, to the admixture of which in certain proportions all their 
tints are due. ‘These he named Oorhodeine, Oocyan, Banded 
Oocyan, Yellow Ooxanthine, Rufous Ooxanthine, a sixth substance, 
giving narrow absorption-bands in the red—the true colour of which 
is not yet decided, and lastly Lichenoxanthine. It would be out 
of place here to particularize their chemical properties, and it is 
enough to say that they are closely connected either with hemo- 
globin or bile-pigments, and in many respects resemble the latter 
more than do any other group of colouring-matters, but do not 
actually agree with them. ‘The first is perhaps the most important 
of all the seven, because it occurs more or less in the shells of so 
great a number of eggs that its entire absence is exceptional, and 
it is of a very permanent character, its general colour being of a 
peculiar brown-red. The second and third seem when pure to be 
of a very fine blue, but the spectrum of the former shews no 
detached bands, while that of the latter has a well-marked detached 
absorbent-band near the red end, though the two are closely related 
since they yield the same product when oxidized. The fourth and 
fifth substances supply a bright yellow or reddish-yellow hue, and 
the former is particularly characteristic of eggs of the Emxus, 
Dromzxus, giving rise when mixed with Oocyan to the fine malachite- 
green which they possess, while the latter has only been met with 
in those of the Tinamous, Zinamidx, in which it should be 
mentioned that oorhodeine has not been found, or perhaps in those 
of a CASSOWARY, Casuarius, and when mixed with Oocyan produces 
a peculiar lead-colour. The sixth substance, as before stated, has 
not yet been sufficiently determined, but it would seem in combina- 
tion with others to give them an abnormally browner tint ; and the 
seventh appears to be identical with one which occurs in greater or 
less amount in almost all classes of plants, but is more especially 
abundant in and characteristic of lichens and fungi. There isa 
possibility, however, of this last being in part if not wholly due to 
the growth of minute fungi, though Mr. Sorby believed that some 
such substance really is a normal constituent of the shell of eggs 
having a peculiar brick-red colour. He was further inclined to 
over them in silence to exposing their inefficiency. A great number of rare” 
eggs are also figured in various journals, as the Proceedings of the Zoological 
Society, Nawmannia, the Journal fiir Ornithologie, and Thé Ibis. 
1 Cf. Wilke, Nawmannia, 1858, pp. 393-397, and C. Leconte, Revue e 
Magasin de Zoologie, 1860, pp. 199-205. 
