300 MONTGOMERY. [Vou. XII. 
adaptation ; while if the environment is becoming less complex, 
then the structure of the organism must become less intricate. 
For if the environmental action become more complex while 
the structure of the organism remains as it was, or becomes 
more simple, then the latter can no longer continue to exist ;! or 
if the environment become less complex in its action while the 
organism’s structure either remains as it was or becomes more 
complicated, its extinction must be brought about. These 
relations of changes in the environment to changes in the 
structure of the organism, with reference to their effect on 
the existence of the latter, may be graphically represented as 
follows : 
( + Progress 
development of -= continued existence of organism. 
ahs ip roy 
complexity of + Regress. 
environment development of ¢= extinction of organism. 
organism 
+ Progress. 
development of -= extinction of organism. 
mea Sat 
complexity of + Regress. 
environment development of -= continued existence of organism. 
organism 
Accordingly, when the phenomena of variation are more 
clearly understood, and the direction and quantitative amount 
of change in the environment can be determined, then it will 
be possible to predict the future of a given organism. 
Now variation, as I have tried to explain it, expresses a want 
of correlation between the several organs; and such an inter- 
ruption of the correlation can be caused only by the agency of 
a change of environment. Accordingly, it is permissible to 
state of a variable organ that it is not in complete correlation 
with its fellow organs ; and consequently, further, that some 
change is occurring, or has taken place, in the environment. 
SD) 
1 A possible example of such a case is that afforded by the now extinct group 
of Ammonites. 
