INTRODUCTION. 
19 
Differences of this kind, between organized beings, are w^hat are termed varieties. 
There is no proof that all the differences which now distinguish organized beings are 
such as may have been produced by circumstances. All that has been advanced uj 3 on 
this subject is hypothetical : experience seems to show, on the contrary, that, in 
the actual state of things, varieties are confined within rather narrow limits ; and, 
so far as we can retrace antiquity, we perceive that these limits were the same as at 
present. 
We are then obliged to admit of certain forms, which, since the origin of things, 
have been perpetuated without exceeding these limits ; and all the beings appertaining 
to one of these forms constitute what is termed a species. Varieties are accidental 
subdivisions of species. 
Generation being the only means of ascertaining the limits to which varieties may 
extend, species should be defined the reunion of individuals descended one from the 
other, or from common parents, or from such as resemble them as closely as they 
resemble each other ; but, although this definition is rigorous, it will be seen that its 
application to particular individuals may be very difficult when the necessary experi- 
ments have not been made.* 
To recapitulate, — absorption, assimilation, exhalation, developement, and generation, 
are the functions common to all living beings ; birth and death, the universal limits of 
their existence ; a porous, contractile tissue, containing within its laminae liquids or 
gases in motion, the general essence of their structure ; substances almost all 
susceptible of being converted into liquids or gases, and combinations capable of easy 
transformation into one another, the basis of their chemical composition. Fixed 
forms, and which are perpetuated by generation, distinguish their species, determine 
the complication of the secondary functions proper to each of them, and assign to them 
the office they have to fulfil in the grand scheme of the universe. These forms 
neither produce nor change themselves ; the life supposes their existence ; it can exist 
only in organizations already prepared ; and the most profound meditations, assisted 
by the most delicate observations, can penetrate no further than the mystery of the 
pre-existence of germs. 
DIVISION OF ORGANIZED BEINGS INTO ANIMALS AND VEGETABLES. 
Living or organized beings have been subdivided, from the earliest times, into ani- 
mate beings, or those possessing sense and motion, and inanimate beings, which enjoy 
* That insurmountable difficulties oppose the rigid determination of 
species, and, consequently, render even the definition of the term 
impossible, except in a very vague and loose manner, will readily 
appear on consideration of some of the phenomena presented. 
The prevalent idea is, that a species consists of the aggregate of 
individuals descended from one original parentage, which alone are 
supposed to be capable of producing offspring that are prolific inter 
se ; and that when individuals, not of the same pristine derivation, 
interbreed, the hybrids are necessarily mules, which are either quite 
sterile, or at most can only propagate with individuals of unmixed 
descent. But it so happens, that every possible grade of approxi- 
mation is manifested, from the most diverse races, to those which are 
utterly undistinguishable ; while, even in the latter case, urgent ana- 
logies, notwithstanding, sometimes forcibly indicate a separateness of 
origin ; as when a series of analogous races inhabiting distant regions 
are compared together, some of which are obviously different, others 
doubtfully so, and some apparently identical. And it remains to be 
shown whether such intimately allied races as some of these, even if 
not descended from a common stock, (which of course cannot be 
ascertained), would not produce hybrids capable of transmitting and 
perpetuating the mingled breed. It is true that Cuvier guards 
against this contingency, in the wording of his definition ; and that 
most naturalists would concur in regarding such miscible races, how- 
ever dissimilar, as varieties merely of the same ; but a question 
arises, whether there be not different degrees of fertility in hybrids, 
corresponding to the amount of affinity, or physiological accordancy^ 
subsisting betwixt the parent races ; it being only within a certain 
sphere of that affinity that they can be produced at all : besides which, 
as hybrids are seldom exactly intermediate, and in some instances 
(particularly among multiparous races) have been known to resemble 
entirely one or the other parent, it may be presumed that this circum. 
stance would also materially affect their capability of propagation* 
Experiments are needed to solve tliis important problem, though tliere 
is every reason to suspect that the following proposition will eventu- 
ally gain the general assent of naturalists, viz., that while considerable 
dissimilarity does not of necessity unply specrftcal diversity, the con- 
verse equally holds, that absolute resemblance fails of itself to con- 
stitute specijical identity. — Ed. 
c 2 
