66 EXPERIMENTAL EVOLUTION LECT. 



features which distinguish them from the similar 

 compounds. Albumen is not the same in all eggs, 

 for instance, in those of the hen, turkey, and duck ; 

 and the flesh of fishes is different from that of 

 mammals or birds. It even follows from Prof. 

 Gautier's experiments that there are differences in the 

 same animal at different times of life, and differences 

 according to the mode of life and nutrition. For 

 instance, if the meat of oxen, fed in the ordinary 

 manner upon hay and grass in the pasture, is com- 

 pared with that of oxen which have been fed and 

 rapidly fattened with the refuse of beet-sugar fac- 

 tories, as is often done in France and Germany, there 

 is not only a difference in the taste and flavour of the 

 steaks or roasts, there is also a chemical difference 

 which is easily detected. While the flesh of the 

 pasture-oxen rapidly dissolves in water and hydro- 

 chloric acid, that of the oxen fed on beet-refuse 

 dissolves very slowly and incompletely ; the greater 

 part does not become transformed into syntonin, and 

 in this respect it resembles the flesh of calves, veal 

 being very refractory to the action of dilute hydro- 

 chloric acid. 



I may have been dwelling rather a long time on 

 M. Gautier's experiments, but they seem to me very 

 interesting and suggestive. Of course we do not yet 

 know anything about the cause of variation, but it is a 



