"You now doubtless conceive how important are the considerations
which I have just exposed to you, and how wrong you would be if, in
devoting yourself to the study of animals or of plants, you should
seek to see among them only the multiplied distinctions that we have
been obliged to establish; in a word, if you should confine
yourselves to fixing in your memory the variable and indefinite
nomenclature which is applied to so many different bodies, instead
of studying Nature herself--her course, her means, and the constant
results that she knows how to attain."

On the next fly page are the following words: _Esquisse d'une
Philosophie zoologique_.

IV. _Lamarck's Views as published in 1806._[177]

"Those who have observed much and have consulted the great
collections, have been able to convince themselves that as gradually
as the circumstances of their habitat, of exposure to their
surroundings, of climate, food, mode of living, etc., have changed,
the characters of size, form, of proportion between the parts, of
color, of consistence, of duration, of agility, and of industry have
proportionately changed.

"They have been able to see, as regards the animals, that the more
frequent and longer sustained use of any organ gradually strengthens
this organ, develops it, enlarges it, and gives it a power
proportional to the length of time it has been used; while the
constant lack of use of such an organ insensibly weakens it, causes
it to deteriorate, progressively diminishes its faculties, and tends
to make it waste away.[178]

"Finally, it has been remarked that all that nature has made
individuals to acquire or lose by the sustained influence of
circumstances where their race has existed for a long time, she has
preserved by heredity in the new individuals which have originated
from them (_elle le conserve par la generation aux nouveaux
individus qui en proviennent_). These verities are firmly grounded,
and can only be misunderstood by those who have never observed and
followed nature in her operations.

"Thus we are assured that that which is taken for _species_ among
living bodies, and that all the specific differences which
distinguish these natural productions, have no absolute _stability_,
but that they enjoy only a relative _stability_; which it is very
important to consider in order to fix the limits which we must
establish in the de