EGGS 1S7 



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 Mi-. 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, Ptufous 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 hsemo- 

 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 iine 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 EaiEUS, 

 Dromdsus, giving rise when mixed Avith Oocyan to the fine malachite- 

 green which they possess, while the latter has only been met with 

 in those of the TiNAivious, Tinamidse, 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 is a 

 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, Naumannia, the Journal fiir Ornithologie, and The Ibis. 



^ Cf. "Wilke, Naumannia, 1858, pp. 393-397, and C. Leconte, Revue el 

 Magasin de Zoologie, 1860, pp. 199-205. 



