108 Proceedings of Royal Society of Edinburgh. [sess. 
(2) “ Characters can only be inherited in so far as their rudiments 
(anlagen) are already given in the germinal protoplasm (keim- 
plasma).” 
(3) “ Modifications which are wrought upon the formed body, in 
consequence of external influences, must remain limited to the 
organism in which they arose.” 
(4) “ So must it be with mutilations, and with the results of use 
or disuse of parts of the body.” 
(5) “ No such modifications of the soma (affected by environ- 
ment or by use and disuse) can be transmitted to the germ-cells, 
from which the next generation springs. They are, therefore, of 
no account in the modification of the species.” 
(6) “The only principle that remains for the explanation of the 
modification of the species, is direct germinal variation.” The 
intermingling of the sex elements is the origin of the variations, 
on which natural selection in the usual way operates. 
Weismann’s position is thus clear and definite. The sole foun- 
tain of specific change is found in the intermingled nuclear 
plasma of the sex-cells. The environment does make dints upon 
the organism, but only upon its soma ; the reproductive cells, 
through which alone the variation could be transmitted, are 
unaffected. The effects of use and disuse may be marked enough, 
and important for the individual, but they are not transmitted, and 
therefore of no account in the history of the species. The ground 
is taken from under the feet of Lamarckians and Buffonians, and 
the whole burden of progress is laid upon germinal variation in 
sexual reproduction, and upon natural selection. 
And as to the alleged cases of the inheritance of acquired char- 
acters in which we and our fathers have believed, they usually admit 
of one of three rebuffs. They may be entirely fictitious or in some 
cases mere coincidences. The inheritance of a letter branded upon 
the arm, which Aristotle notes, is an extreme type of what His calls 
a handful of anecdotes. Or the apparent inheritance of acquired char- 
acters may be explained in this way ; similar surroundings hammer 
the same change upon successive generations, and we mistake 
reappearance for transmission. The case of Nageli’s Alpine plants 
which seemed to have been thoroughly changed, but lost their 
characters when the influencing conditions were removed, is often 
