180 Darwin and Embryology 
Lamarck’s “acquired characters”? They are variations in genetic 
characters caused in a particular way. There are, in fact, two kinds 
of variation in genetic characters depending on the mode of causa- 
tion. Firstly, there are those variations consequent upon a variation 
in the constitution of the protoplasm of a particular zygote, and 
independent of the environment in which the organism develops, 
save in so far as this simply calls them forth: these are the 
so-called genetic or mutational variations. Secondly, there are 
those variations which occur in zygotes of similar germinal con- 
stitution and which are caused solely by differences in the environ- 
ment to which the individuals are respectively exposed: these are 
the “acquired characters” of Lamarck and of authors generally. 
In consequence of this double sense in which the term “acquired 
characters” may be used, great confusion may and does occur. If 
the protoplasm be compared to a machine, and the external con- 
ditions to the hand that works the machine, then it may be said that, 
as the machine can only work in one way, it can only produce one 
kind of result (genetic character), but the particular form or quality 
(Lamarckian “acquired character’’) of the result will depend upon 
the hand that works the machine (environment), just as the quality 
of the sound produced by a fiddle depends entirely upon the hand 
which plays upon it. It would be improper to apply the term 
“mutation ” to those genetic characters which are not new characters 
or new variants of old characters, but such genetic characters are of 
the same nature as those characters to which the term mutation has 
been applied. It may be noticed in passing that it is very questionable 
if the modern biologist has acted in the real interests of science in ap- 
plying the term mutation in the sense in which he has applied it. The 
genetic characters of organisms come from one of two sources: either 
they are old characters and are due to the action of what we call in- 
heritance or they are new and are due to what we call variation. If 
the term mutation is applied to the actual alteration of the machinery 
of the protoplasm, no objection can be felt to its use; but if it be 
applied, as it is, to the product of the action of the altered machine, 
viz. to the new genetic character, it leads to confusion. Inheritance 
is the persistence of the structure of the machine; characters are 
the products of the working of the machine; variation in genetic — 
characters is due to the alteration (mutation) in the arrangement 
of the machinery, while variation in acquired characters (Lamarckian) 
is due to differences in the mode of working the machinery. The 
machinery when it starts (in the new zygote) has the power of 
grinding out certain results, which we call the characters of the 
organism. These appear at successive intervals of time, and the 
orderly manifestation of them is what we call the life-history of the 
