74 EVOLUTION AND THE 
the influence of Natural Selection as a modifying 
agent is probably much less important than it is 
amongst more active and complex animal forms: and 
in all cases its action in producing change may be 
assisted by ‘spontaneous’ internal changes in the 
molecular activity of certain parts of the organism, 
or by other internal changes more obviously induced 
by modifications in the sum total of ‘external con- 
ditions’ acting upon the organism. 
Each cause of specific modification, however, 
whether acting alone or in concert with one of the 
other producers of internal change, can only come 
into play in subordination to the ever potent laws 
of ‘organic polarity,’ by which a multiplication of 
effects is apt to be induced. 
In addition to these conclusions concerning the 
present order of events, we seem warranted in draw- 
ing the following speculative deductions concerning 
the past:— 
An elemental origin of living matter similar to 
that which takes place at the present day, and, in 
addition, all the related heterogenetic phenomena, 
have probably been taking place on the surface of 
our globe since the far remote period when such 
matter was first engendered. 
The countless myriads of living units which have 
been evolved in different ages of the world’s history 
