CHEMICAL VARIATION 63 



by reasoning we also come to the conclusion that 

 there must be physiological or chemical differences 

 accompanying the anatomical or morphological varia- 

 tions. ^ But Prof. Gautier has tried to appreciate 

 these differences, and to measure them in some 

 way. Notwithstanding the Linnaean axiom con- 

 cerning colour, and the fact that many consider 

 colour variation as of very little import because it is 

 so frequent, Gautier has studied with great care the 

 intimate changes which accompany colour variation. 

 The common grape has been selected by him as 

 his subject, all varieties of grape being varieties 

 of one common stock, however different they may be 

 in many respects ; and after a careful investigation of 

 the colouring matters, he has come to the conclusion 

 that, although they all belong to the same type, and 

 have all been considered as one and the same, they 

 offer important differences. For instance, while some 

 of the pigments are soluble in water, others are not ; 

 while some yield green precipitate with lead salts, 

 others yield a blue one ; while some contain nitrogen, 

 others do not. For instance, again, grapes of the 

 Carignan variety contain a colouring matter of the 

 type C 21 H 20 O 10 , and another which contains C 22 H 24 O 10 . 

 The Grenache variety contains a different matter, 

 C, 3 H 22 O 10 ; Aramon contains C 23 H 18 O 10 ; Teinturier 

 answers to C 22 H 20 O 10 , Petit-Bonschet to C^H^O^, 



