440 
DARWINISM 
CHAP. 
The Non-Heredity of Acquired Characters. 
Certain observations on the embryology of the lower 
animals are held to afford direct proof of this theory of heredity, 
but they are too technical to be made clear to ordinary 
readers. A logical result of the theory is the impossibility of 
the transmission of acquired characters, since the molecular 
structure of the germ-plasm is already determined within the 
embryo; and Weismann holds that there are no facts which 
really prove that acquired characters can be inherited, although 
their inheritance has, by most writers, been considered so prob¬ 
able as hardly to stand in need of direct proof. 
We have already shown, in the earlier part of this chapter, 
that many instances of change, imputed to the inheritance of 
acquired variations, are really cases of selection ; while the very 
fact that use implies usefulness renders it almost impossible to 
eliminate the action of selection in a state of nature. As 
regards mutilations, it is generally admitted that they are not 
hereditary, and there is ample evidence on this point. When 
it was the fashion to dock horses’ tails, it was not found that 
horses were born with short tails ; nor are Chinese women 
born with distorted feet; nor are any of the numerous forms 
of racial mutilation in man, which have in some cases been 
carried on for hundreds of generations, inherited. Neverthe¬ 
less, a few cases of apparent inheritance of mutilations have 
been recorded, 1 and these, if trustworthy, are difficulties in the 
way of the theory. The undoubted inheritance of disease is 
hardly a difficulty, because the predisposition to disease is a 
congenital, not an acquired character, and as such would be the 
subject of inheritance. The often-quoted case of a disease 
induced by mutilation being inherited (Brown-Sequard’s 
epileptic guinea-pigs) has been discussed by Professor Weis¬ 
mann, and shown to be not conclusive. The mutilation itself 
—a section of certain nerves— was' never inherited, but 
new forms. Again, in partlienogenetic females the complete apparatus for 
fertilisation remains unreduced ; but if these varied as do sexually produced 
animals, the organs referred to, being unused, would become rudimentary. 
Even more important is the significance of the “ polar bodies,” as explained 
by Weismann in one of his Essays ; since, if his interpretation of them be 
correct, variability is a necessary consequence of sexual generation. 
1 Darwin’s A nimals and Plants, vol. ii. pp. 23, 24. 
