1891.] 
201 
[Dolbear. 
gle atom of a different substance should accidentally become 
imbedded, either as a constituent or not, it would bring its field 
along with it necessarily and the resultant field of the whole would 
be modified. It could not be quite what it would be in the ab- 
sence of this new constituent, and consequently the reaction upon 
other matter in its neighborhood would be different and the next 
organic molecule formed would need to be a little differently or- 
ganized. Mechanical conditions would necessitate it. Again if 
energy, radiant or conducted, should act for a short time upon 
one part of a molecule it might easily bring about an exchange 
of position among some of the less stable constituents without 
other disturbance and this too would result in a change of the 
configuration of the field and the direction of growth. Every 
change in the collocation and motions among molecules exhibits itself 
in changed properties. Such conditions might properly be spoken 
of as changes in the environment, but it is molecular environ- 
ment, and the difference between this idea and that heretofore 
common is that the molecule produces an environment of its own. 
The space beyond its own geometric boundary, in which it is 
competent to act upon other bodies and compel other bodies to 
conform in a greater or less degree to it. More than that, a new 
constituent in a nearly saturated molecule could not have as firm 
a grip upon the structure as the older constituents could have, 
although it might so modify things while present as to organize 
other molecules in like manner, but slight changes in the neigh- 
borhood might slough off the new acquisition in a subsequent 
generation so there might be a return to the form and qualities 
of the ancestry, that is, reversion to former type would also be a 
mechanical consequence. 
Thus growth, heredity, variation and reversion may be con- 
sidered as the consequence of atoms vibrating in harmonic order, 
each producing its own field in the universal ether and each 
group of atoms constituting a molecule large or small, having a 
field which is the resultant of all the fields of its constituents. 
All of them are molecular properties as much as any one of them 
can be, and growth has been believed for a long time to be a 
property of inorganic molecules. The cause of variation is there- 
fore molecular as truly as isomerism is, a different collocation of 
atoms. It is a chemical problem. 
