Le Dantec 269 
a+Q=nra+R (where a=mass of each single 
specific assimilating substance; Q = mass of the nutritive 
substances absorbed; » = coefficient > 1; and R = mass 
of the substances of refuse), multiplies all these sub- 
stances and preserves to them their original proportions. 
Destruction however, or at least certain destructions, act 
separately on each of these substances and alter the pro- 
portions of the mixture and consequently the characters 
of the plastid.” 2°% 
From this it appears that LeDantec attributes all 
variations which the plastids or organisms in general 
can undergo, to total or partial destructions of the dif- 
ferent, particular plastic substances (a) already present, 
but never to the production of new plastic substances. 
The numbers and characters of plastic substances, which 
participate in the formation of the complex substance 
of the plastid or rather of the organism in general, may 
be different in different species. The difference between 
different species and between different individuals of the 
same species, would consist only in the proportions in 
which the special plastic substances (a) peculiar to this 
species, are united. 
“We are inclined to regard the living substances of 
the plastids as mixtures of different plastic substances, 
the substances (a). The species of the plastids would 
be determined by the nature or quality of these plastic 
substances; their individual peculiarities, their person- 
ality, would depend upon the proportions of the mixture of 
these specific plastic substances. In the same way we must 
regard the individual substances in the higher organisms 
as characterized by a mixture in definite proportions of 
#87 6 Dantec: Traité de Biologie. P. 93. 
