ARE ACQUIRED CHARACTERS HEREDITARY? 335 
Neo-Lamarckism.—Many modifications of the Lamarckian 
hypothesis of the inheritance of acquired characters have been pro- 
posed in recent years. Foremost among those are the ‘“mneme”’ 
theory of Semon and the ‘‘centro-epigenesis”’ theory of Rignano. To 
Semon as to many other biologists the apparent resemblance between 
memory and heredity has seemed significant, and this furnishes the 
basis of his theory. Semon holds that every condition of life, every 
functional activity of an organism leaves a permanent record of itself 
in what he calls an “‘engramme.” If these conditions or activities 
are long continued their engrammes are heaped up and affect heredity. 
Semon does not ask if ‘‘acquired characters” are inherited, but rather 
“Are the hereditary potencies of the germ cells altered by stimuli 
acting on the parental body?” This is a very different thing from 
the inheritance of a particular acquired character, and there is some 
evidence that such stimuli may in rare instances produce changes in 
the hereditary constitution of the germ plasm though these evidences 
are by no means conclusive. 
Temporary effects of environment; “induction.’—On the other 
hand certain changes may be produced in germ cells or embryos which 
last for only a generation or two and then disappear. It is well known 
that plants grown in poor soil are smaller and produce smaller seeds 
than those grown in good soil, and De Vries, Bauer and Harris find 
that such seeds produce smaller plants having smaller seeds than do 
seed of normal size. This is an after effect of poor nutrition which’ 
changes the amount of food material in the seeds and through this the 
size of the plant which develops from the seed, but it does not change 
the hereditary constitution. Woltereck found that in Dapknia there 
is an after effect of cold lasting for one or two generations, and this he 
calls “induction,”’ when the effect lasts for one generation, or “ pre- 
induction” when it lasts for two or three generations. Whitney found 
that rotifers poisoned with alcohol were weaker in resistance to copper 
salts and were less fertile than others, and when brought back to 
normal conditions the first generation was weak but the second was 
normal. On the other hand Stockard finds that the injurious effects 
of alcohol on guinea pigs persist through two or more generations. In 
man alcohol may have an “induction” eect on offspring, but fortu- 
nately it does not seem to alter hereditary constitution. Probably of a 
similar character are Sumner’s results; he found that mice raised in the 
cold have shorter tails than those raised in higher temperatures and this 
modified character appears in the next generation. If thisis an after 
effect or “induction” it should disappear in the following generations. 
