74 
been taken for granted as a fundamental 
truth. It may be tersely expressed in the 
following form: 
1. Heredity is a fundamental law of all 
organisms. 
2. Variation is an acquired law of or- 
ganism, and is determined by the interac- 
tion of the heterogenous environment upon 
the otherwise uniformly operating organic 
matter. 
It is the validity of these two proposi- 
tions that I would call in question and dis- 
cuss. Is heredity acquired? When the 
attempt is made to state with precision 
what takes place in the phenomena of or- 
ganic evolution the question arises: What 
is the relation which variation bears to 
heredity as a factor in the case? Which is 
fundamental ; which is acquired? 
In order to make the real point of the 
case clear, let us take an analogy from the 
field of physics. In astronomical pheno- 
mena the planetary bodies are observed to 
be in rotary motion about the sun and 
about their own axes; is the rotary motion 
fundamental or acquired? The first law of 
Newton is this: “‘ Every body continues in 
its state of rest, or of uniform motion in a 
straight line, except in so far as it is com- 
pelled by force to change that state.” And 
force is defined as ‘‘ whatever changes the 
state of rest or uniform motion of a body.” 
According to these accepted laws of me- 
‘chanics, rotary motion must be regarded as 
secondary to direct motion or translation. 
In order to explain rotary motion, the law 
of gravity is brought in, and the circular 
motion is defined as the resultant of the 
motion of translation adjusted to the gravi- 
tation of the masses of matter in motion. 
From this analogy the real nature of 
the problem may be inferred when we ask 
what is the relation which heredity bears 
to variation in the field of biology? If it 
be a fundamental law of organisms to re- 
peat themselves in cycles of generation, to 
SCIENCE. 
[N.S. Vou. VI. No. 133. 
adopt the analogy of mechanics and 
physics, it is essential to postulate some 
force to account for any deviation from 
such hereditary cycles. If, on the other 
hand, variation be the primary law of 
organism, the postulated force is required 
to account for the repetition: such a force 
would operate first in checking the varia- 
tion. It will thus be seen that the ex- 
planation of the phenomena of life will be 
greatly modified according as one or other 
of these hypotheses be assumed to be true. 
If we look back over the history of 
opinions in natural history we discover 
that a century ago the whole philosophy 
of organisms was dominated by the Cu- 
vierian notion that species are immutable ; 
i. e., that the cycles of phenomena pre- 
sented in the development of an individual 
organism in the passage from the embryo 
to the adult stages are the same for all 
members of a species; that this uniformity 
in expression of development by the indi- 
vidual is the mark or distinguishing char- 
acteristic of each species, and therefore 
that variations, or departures from this 
fixed law, are accidents due to the disturb- 
ing effects of outward environment upon 
the individual, and cannot be transmitted 
to offspring by the ordinary laws of he- 
redity. It was this conception of the im- 
mutability of species which made ‘special 
creation’ of species seem to be a rational 
theory, and it was the calling in question of 
the immutability of species which was sup- 
posed to limit the capacity of creative 
force in the universe. 
Lamarck adyanced the theory that 
species are not fixed, but are mutable; and 
' he was supposed to be attacking the very 
foundations of natural history; he was 
laughed at and his theory was, for the time, 
silenced by the weight of authority and 
the common opinion of naturalists. One 
of the strongest arguments used against 
his theory was the very fact of species as 
