64 EXPERIMENTAL EVOLUTION LECT. 



and Camay to C 20 H 20 O 10 . This shows that the slight 

 external differences which are peculiar to each sort or 

 variety, derived from the common stock by selection 

 and culture, arc accompanied by important chemical 

 variations. The above-mentioned differences illus- 

 trate the fact. It must be added, also, that other 

 differences are to be met with differences in the 

 amount and nature of sugar, tannin, &c. 



These results determined Prof. Gautier to investi- 

 s gate an important matter which is closely related 

 to the foregoing topics, and he has examined the 

 colouring-matter of hybrid forms. For instance, 

 Petit-BouscJiet is the result of the impregnation of 

 Teinturier by Aramon pollen ; and the question to be 

 solved is the following : Is Petit- Bouscket colouring- 

 matter identical with that of one of its parents, or 

 intermediate between both, or is it entirely different ? 

 Direct analysis shows that the second supposition 

 is true. Petit-Bonschet colouring-matter is nearly 

 exactly intermediate between those of its parents, 

 and its composition is the arithmetical mean between 

 those of the two stocks from which it is derived. 

 Another important fact which has been pointed out 

 by Gautier is that all colouring-matter which may 

 be found in grapes, when subjected to the influence 

 of potash, splits into two sorts of chemical com- 

 pounds ; two of them are constant, and invariably 



