xvi THE EVOLUTION OF LIFE 
this no living thing can come into being. They 
also were heterogenists in the wide sense given to 
this term by Burdach, and their theoretical views 
would not have allowed them to believe in what we 
have been speaking of as Archebiosis. 
The term Heterogenesis is, however, always used 
by me in the more limited sense originally given to 
it by Burdach in his definition, as the class name for 
processes by which living things arise from the 
matter of pre-existing organisms éelonging to a 
totally different speczes. ‘When such a_ process 
occurs, it is a matter of altogether secondary import- 
ance whether the individualisation of a portion of 
the matter of an organism (with power of inde- 
pendent development) takes place during the life of 
such organism or after its death—since the death of 
any of the higher organisms does not at once entail 
the death of the matter entering into its composition. 
Its constituent parts continue to live for a time, and 
gradually, at different intervals, they lapse into the 
condition of mere dead matter. 
When this stage comes, when the living substance 
is dead, we still have to do with organic matter com- 
posed of highly complex molecules—though now it is 
soluble in water. But when such matter has given 
up its semi-solid form and has undergone solution, it 
is in no sense, in accordance with commonly re- 
ceived views, to be regarded as living; so that if, in 
a solution thus formed, the evidence were to point 
to the de xzovo origin therein of living units, we 
might quite legitimately speak of it as a process of 
Archebiosis. Although the matter in solution may 
