22 HEREDITY, AND THE ORIGIN OF SPECIES. 
tives of simple leaved ancestors, and are therefore capable 
of easy observation. With these facts in hand the possi- 
bility suggests itself that we might be able to distinguish 
between a structure recently arisen and one which was 
borne by a related species for thousands of years, but 
the exactness of such estimates is a matter of conjecture. 
It seems to be taken for granted by a great number of 
workers interested in this subject, that species showing 
wide variations of the organs are the ones most likely to 
offer a high frequency of mutations, and my correspond- 
ents in various parts of the country are constantly calling 
attention to these forms under such a mistaken impression. 
As a matter of fact we may confidently expect that the 
species which show the greatest variation, or are eversport- 
ing, are the youngest. 
Now havirtig obtained the result just described we find 
ourselves face to face with one of the most interesting and 
difficult questions in heredity. If the newly arisen mutant 
forms are more widely variable than the older ones, how do 
they ultimately become narrowed? If the greater number 
of species originated by mutation, as we confidently be- 
lieve they did, then they must have shown a much wider 
range of variability than they do at present; by the opera- 
tion of what agency has variability been decreased, and 
correlations made more strict? At the present time I am 
compelled to say that I can not make an intelligent sugges- 
tion. Again if new characters vary widely at first, and lose 
this power, would it be possible to estimate the age of any 
given character of a species from the degree of variability? 
The author of the investigations just noted suggests that 
the best prospect for evidence of value upon this point 
might be obtained by a comparative statistical study of 
more recent types of structures in the foliar or reproduc- 
tive organs, and of older forms that have come down from 
