336 READINGS IN EVOLUTION, GENETICS, AND EUGENICS 
Kammerer found that salamanders with black and yellow spots 
when reared on yellow soil gradually lose their black color, becoming 
more yellow, and their young continue to grow more yellow until 
finally almost all black may disappear. The offspring of such sala- 
manders are said to be more yellow than normal; but this work has 
been called in question and needs confirmation. Even if confirmed 
the result may be an after effect or “induction” which would soon 
disappear under usual conditions, and there is no evidence that it is 
really inherited. 
Such cases are not instances of true inheritance; they do not 
signify a change in the hereditary constitution but an influence on the 
germ cells of a nutritive or chemical sort comparable with what takes 
place when fat stains are fed to animals; the eggs of such animals are 
stained, and the young which develop from such eggs are also stained, 
though the germinal constitution remains unchanged. The very fact 
that the changed condition is reversible and that it disappears within 
a short time is evidence that it is not really inherited. 
In conclusion: (1) Developed characters, whether “acquired” 
or not, are never transmitted by heredity, and the hereditary constitu- 
tion of the germ is not changed by changes in such characters. (2) 
Possibly environmental stimuli acting upon germ cells at an early 
stage in their development may rarely cause changes in hereditary 
constitution, but changes produced in somatic cells do not cause 
corresponding changes in the hereditary constitution of the germ cells. 
(3) Germ cells like somatic cells may undergo modifications which are 
not hereditary; if starved they may produce stunted individuals and 
this effect may last for two or three generations; they may be stained 
with fat stains and the generation to which they give rise be similarly 
stained; they may be poisoned with alcohol or modified by tempera- 
ture and such influence be carried over to the next generation without 
becoming hereditary. All such cases are known as “induction” and 
many instances of the supposed inheritance of acquired characters 
come under this category. (4) Environment may profoundly modify 
individual development but it does not generally modify heredity. 
THE OTHER SIDE TO THE QUESTION 
[It will have been noted that the chief objection to the idea of the 
possibility of acquired characters being inherited comes to us as a 
heritage of the rather extreme Weismannian concept of the “germ 
