The Making of Species 
fascinating though it be, is not one that can be 
discussed adequately in a general work on 
evolution. Those interested in the subject are 
referred to Professor Thomson’s Heredzty, and 
to the address given by Professor E. B. Wilson, 
of Columbia University, before the American 
Association for the Advancement of Science, 
which was fully reported in the issue of Sczence, 
dated January 8, 1909. 
Stated briefly, then, our conception is, that 
the fertilised egg is composed of a number of 
entities, to which we have given the name 
“biological molecules,” because in certain 
respects their behaviour is not unlike that of 
chemical molecules. 
The units which compose these molecules, 
being made up of protoplasm, are endowed with 
all the properties of life, including the inherent 
instability which characterises all living matter. 
We suggest that the continuous or fluctuating 
variations that appear in the adult organism may 
be the result of individual differences in the 
biological ‘‘atoms” that compose the molecule. 
Discontinuous variations, or mutations, on the 
other hand, may be the result of a rearrangement 
of the atoms within the biological molecule. 
Upon what causes this rearrangement it would 
not be very profitable to speculate in the present 
state of our knowledge. To do this would be to 
inquire into the cause of a re-grouping of entities 
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