JAN. 1907. 
THE ORIGIN OF SPECIES. 
7 
The era now dawning presents ns with two leading rival 
theories. From Darwin and Wallace we have received the 
theory of Natural Selection, which has been powerfully sup- 
ported by Spencer, Huxley, Haeckel, Weismann, Dohrn, and many 
others. This theory and its triumphs are familiar history. 
In 1901, Hugo be Vries, a distinguished botanist of Amster- 
dam, brought forward his famous Mutation-theory, based upon 
''Experiments and Observations on the Origin of Species in the 
Plant Kingdom." 
This work of De Vries is truly a great achievement, rising 
above any other that has appeared since Darwin's ''Origin of 
Species." It is not only comprehensive in scope, consistent in its 
logic, and charming in style, but it is also epoch-making in its 
method of research. In this latter respect it sets an example which 
is having a world-wide influence — emphasizing as it does the 
supreme importance of studying livijig organisms and of -keeping 
observations and experiments running continuously through a long 
sequence of generations. 
This is the method of the new era in biology — steady unbroken 
continuity in experiment under controlled culture. Here the 
example of Mendel, De Wies, and a few others, will be potent for 
many years to come. 
As to the" real merit of the theory of mutation, only extended 
research can bring a final decision. In dealing with such a 
theory, we must grasp clearly its fundamental conceptions. The 
whole superstructure stands or falls with them. The 
central foundation-idea of this Mutation-theory is that of 
unit-characters. The species represents always a definite number 
of distinct unit-characters, each as distinct and independent as are 
the elements of a chemical compound. Consequently all upward 
progress in the organic world depends upon adding nezv unit-char- 
acters. Furthermore, these unit-characters are held to be essen- 
tially unchangeable, and hence the species compounded of them are 
viewed also as essentially immutable. A unit-character, it is true, 
may undergo transmutation, i. e., it may become a whollv new unit- 
character. Such transmutation, however, is always sudden, never 
by slow intermediate degrees. Any slow and gradual transition, 
such as Darwin and Wallace maintained, never under any circum- 
stances, according to De Vries, could lead to the formation of a 
new species. The utmost that could be attained by such variation 
