THE FOUNTAIN OF CHANGE 243 
to reach certainty in regard to this simple point, 
but there is no harm in asking, as Dr. Gates does, 
whether the white man may have originated from a 
black race by a “ tetraploid mutation and its conse- 
quences.” The nuclear change need not, of course, 
affect the number of the chromosomes; it may 
affect shape and size and structure. More funda- 
mentally—but no longer visibly—a chromosome 
may undergo a change in its stereochemic archi- 
tecture or in its functional powers. We know of 
remarkable mutations in bacteria, which some- 
times change suddenly in their physiological prop- 
erties, = 
The mutation theory is concerned with the origin 
of new characters, and Mendelism is concerned with 
their behavior in inheritance; so the two theories 
touch, and it is interesting to notice Dr. Gates’ 
position, In the first place, it seems clear that there 
is no warrant for supposing that G:nothera lamarcki- 
ana has had a mixed ancestry and that its mutabil- 
ity (still unexhausted ) is a result of this. Mutations 
may occur apart altogether from crossing, though 
crossing may increase their frequency or even 
initiate a condition of germinal instability. In the 
second place, the Mendelian classification of all new 
characters into dominants (due to the addition of a 
factor) and recessives (due to the loss of a factor) 
is much too hard and fast to cover all the facts. 
Germinal changes are of many and diverse kinds, 
and are not exhausted by addition or loss of unit 
factors. Some mutations illustrate Mendelian 
