MEMOIR OP BARON HALLER. 49 



red, black, green, and blue, in the order just enu- 

 merated ; and all produced by the heart, somewhat 

 assisted by external heat. It is by the heart, because 

 fish in the frozen seas of the north manifest almost 

 every colour, and because heat without the aid of 

 the heart will not do it. The chick is much retarded 

 and dies, if the egg continues white. Heat again 

 helps somewhat, since it is true that the most 

 brilliant and beautiful colours of quadrupeds, birds, 

 fishes, shells, and even flowers, are usually found 

 in warm climates. In vegetables it is heat alone 

 which confers the colour; at first they are white, 

 and the sun effects all the subsequent changes. 



Tastes and odours arise with the colours, or very 

 shortly after them. The bile is green before it is 

 bitter; but the bitterness is soon afterwards per- 

 ceptible, and the colouring particles are apparently 

 the same with those which excite the taste and the 

 smell. 



Pass we now to the mechanism which produces 

 the various forms of the different parts. The most 

 simple, and at the same time the most efficacious 

 instrument is unequal increase. An animal no 

 longer resembles itself when some of its organs 

 diminish and become extinct, whilst the others in- 

 crease and are developed, or when some increase 

 to a great extent, whilst the rest make only a slow 

 progress. It is thus the chick changes in relation 

 to the yolk. During the early period of incubation 

 the chick is small ; the internal viscera are yet in- 

 visible, but an enormous appendage of these same 



