Distinction Between Species and Varieties. 579 
is a fundamental antithesis between ancient and recent 
characters, which finds its expression both in the phe- 
nomena of specific differentiation, and in those of arti- 
ficial hybridization; for on the one hand forms can arise 
from others without the production of new factors, simply 
by the transference of factors already present into another 
condition, as from latent to active; and on the other hand, 
by the genuine appearance of new elementary characters. 
Progress in organization is due to the latter process, 
whilst the former is to a large extent the cause of the di- 
versity of organic life. 
If we compare this experimental result with the above 
theoretical considerations, we may assume that the dis- 
tinction between older and younger characters consists 
in the difference between the formation of a new factor 
and the transposition of factors already present. On 
the basis of the doctrine of creation the origin of new 
units must be explained as being due to a supernatural 
cause, but no one has as yet applied this theory to the 
change in position of factors already present. Moreover 
in the light of the idea of evolution also the antithesis 
mentioned has its real and full significance. 
It would lead me too far to analyze here the concep- 
tions of other authors on these points, but such an anal- 
ysis has led me to the conviction that the difference be- 
tween the formation and the transposition of factors cor- 
responds closely to the difference which the best system- 
atists consider to exist between species and varieties. 1 
A form which owes its origin to the production of a new 
internal factor is to be regarded as a species ; a form 
which owes its peculiarity merely to the change in con- 
dition of a factor already present is to be regarded as a 
1 See also Vol. I, p. 185, and Vol. II, pp. 71-72. 
