G. GENERAL NATURAL HISTORY AND ZOOLOGY. 305 



matter of leaves, has lately rendered a similar service in 

 reference to the coloring matter of the egg of the bird, 

 in a paper presented to the Zoological Society of London. 

 He remarks that, although the eggs of the bird appear 

 to be of almost unlimited variety, all this apparent con- 

 fusion is due simply to a variation in the relative and to- 

 tal amount of a limited number of definite and well-marked 

 substances. 



Previous to his inquiry, the only suggestions made in re- 

 gard to this matter of color were that the redder tints w^ere 

 due to altered blood, passing through the swollen vessels of 

 the oviduct, and that both the redder and greener tints are 

 due to bile pigments, and perhaps derived from the faeces in 

 the cloaca. Mr. Sorby, indeed, finds good physical evidence 

 to prove that the characteristic coloring matters in eggs are 

 closely connected either with haemoglobin or bile pigments, 

 but not in the manner suggested b}^ previous writers. He 

 thinks that the coloring of the eggs is due to definite physi- 

 ological products, and not to accidental contamination with 

 substances whose function is altogether different. 



So far Mr. Sorby has found seven well-marked substances, 

 one identical with a coloring matter met with in nearly all 

 groups of plants, from the lowest to the highest ; the rest he 

 has not been able to identify with any found elsewhere. All 

 these seven substances are insoluble in water, but soluble in 

 absolute alcohol, and sometimes in chloroform or carbon bi- 

 sulphide. Some are extremely permanent, and resist the ac- 

 tion of powerful reagents ; others are so unstable that they 

 are not only rapidly changed by acids and other agents, but 

 are even partially decomposed by evaporating tlieir solutions 

 to dryness at a gentle heat. 



The method adopted by jMr. Sorby in his inquiries was to 

 actually separate the coloring matter from the shell, by vari- 

 ous processes detailed by him, as they were subjected to va- 

 rious critical chemical examinations. The substances found 

 by him are as follows : 



First, Oorhodeine. This he considers as the most important 

 and interesting of all the coloring matters, a very small quan- 

 tity being recognized without any difiiculty even when mixed 

 with a large amount of colored impurities. It also occurs, in 

 a larger or smaller amount, in the shells of so great a number 



