JAN. 1907. 
THE ORIGIN OF SPECIES. 
9 
essentially upon food-conditions ; upon them depends the forma- 
tion of improved races, especially in agriculture. Not only 
species, but also varieties arise by mutation." 
(7) "Species have not arisen through gradual selection, con- 
tinued for hundreds or thousands of years, but by jumps (stufen- 
zveise) through sudden though small, transformations. In contrast 
with variations which are changes advancing in a linear direc- 
tion, the transformations to be called mutations diverge in new 
directions. They take place, then, so far as experience goes, with- 
out definite direction." (Vol. i, p. 150). 
(8) "Species-forming variability must be orderless. The 
assumption of a definite variation-tendency which would condition, 
or even favor, the appearance of adaptive modifications, lies out- 
side the pale of the natural science of to-day. In fact, the great 
advantage of Darwin's doctrine of selection lies in this, that it 
strives to explain the whole evolution of the animal and plant 
kingdoms without the aid of supernatural presuppositions. 
According to this doctrine, species-forming variability goes on 
without regard to the qualification of the new species for maintain- 
ing themselves in life. It simply supplies the struggle for exist- 
ance with the material for natural selection. Whether this selec- 
tion takes place betwen individuals, as Darwin and Wallace sup- 
posed, or decides between whole species, as the mutation-theory 
demands, ultimately it is, in either case, simply the ability for 
existence under given external conditions that decides upon the 
permanence of the new form." (p. 180). 
The fundamentals in the mutation theory, then, are : 
1. Every species consists of a fixed number of unit-characters. 
2. The species and the component units are alike sudden in 
origin and unchanging in type. 
3. Old characters may be suddenly transmuted into new ones, 
but between the two there is always a gulf of absolute discontin- 
uity, with no possible bridge of gradual modification. 
4. Continuous intergradations may connect a species with 
an improved race, but never one species with another species. 
5. Species-formation is kaleidoscopic, i. e., chance-wise in 
direction, never resulting from a tendency to vary in any one 
determinate direction. 
6. Natural selection can not give origin to new species ; it 
can only weed out from those already in existence such as are 
incapable of sustaining themselves. 
