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 chauges. 
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 whep 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 
D 
