THE "PHILOSOPHIE ZOOLOGIQUE"
Lamarck's mature views on the theory of descent comprise a portion of
his celebrated _Philosophie zoologique_. We will let him tell the story
of creation by natural causes so far as possible in his own words.
In the _avertissement_, or preface, he says that his experience has led
him to realize that a body of precepts and of principles relating to the
study of animals and even applicable to other parts of the natural
sciences would now be useful, our knowledge of zoölogical facts having,
for about thirty years, made considerable progress.
After referring to the differences in structure and faculties
characterizing animals of different groups, he proceeds to outline his
theory, and begins by asking:
"How, indeed, can I consider the singular modification in the
structure of animals, as we glance over the series from the most
perfect to the least perfect, without asking how we can account for
a fact so positive and so remarkable--a fact attested to me by so
many proofs? Should I not think that nature has successively
produced the different living beings by proceeding from the most
simple to the most compound; because in ascending the animal scale
from the most imperfect up to the most perfect, the organization
perfects itself and becomes gradually complicated in a most
remarkable way?"
This leads him to consider what is life, and he remarks (p. xv.) that it
does not exist without external stimuli. The conditions necessary for
the existence of life are found completely developed in the simplest
organization. We are then led to inquire how this organization, by
reason of certain changes, can give rise to other organisms less simple,
and finally originate creatures becoming gradually more complicated, as
we see in ascending the animal scale. Then employing the two following
considerations, he believes he perceives the solution of the problem
which has occupied his thoughts.
He then cites as factors (1) use and disuse; (2) the movement of
internal fluids by which passages are opened through the cellular tissue
in which they move, and finally create different organs. Hence the
_movement of fluids in the interior of animals_, and the _influence of
new circumstances_ as animals gradually expose themselves to them in
spreading into every inhabitable place, are the two general causes which
have produced the different animals in the condition we now see them.
Meanwhile he perceived the importance of the preservation by heredity,
though he nowhere uses that word, in the new individuals reproduced of
everything which the results of the life and influencing circumstances
had caused to be acquired in the organization of those which have
transmitted existence to them.
In the _Discours préliminaire_, referring to the _progression_ in
organization of animals from the simplest to man, as also to the
successive acquisition of different special organs, and consequently of
as many faculties as new organs obtained, he remarks:
"Then we can perceive how needs (_besoins_), at the outset reduced
to nullity, and of which the number gradually increases, have
produced the inclination (_penchant_) to actions fitted to satisfy
it; how the actions, becoming habitual and energetic, have caused
the development of the organs which execute them; how the force
which excites the organic movements may, in the simplest animals, be
outside of them and yet animate them; how, then, this force has been
transported and fixed in the animal itself; finally, how it then has
become the source of sensibility, and in the end that of acts of
intelligence.
"I shall add that if this method had been followed, then _sensation_
would not have been regarded as the general and immediate cause of
organic movements, and it would not have been said that life is a
series of movements which are executed in virtue of sensations
received by different organs; or, in other words, that all the vital
movements are the product of impressions received by the sensitive
parts.[179]
"This cause seems, up to a certain point, established as regards the
most perfect animals; but had it been so relatively to all living
beings, they should all be endowed with the power of sensation. But
it cannot be proved that this is the case with plants, and it cannot
likewise be proved that it is so with all the animals known.
"But nature in creating her organisms has not begun by suddenly
establishing a faculty so eminent as that of sensation: she has had
the means of producing this faculty in the imperfect animals of the
first classes of the animal kingdom," referring to the Protozoa. But
she has accomplished this gradually and successively. "Nature has
progressively created the different special organs, also the
faculties which animals enjoy."
He remarks that though it is indispensable to classify living forms, yet
that our classifications are all artificial; that species, genera,
families, orders, and classes do not exist in nature--only the
individuals really exist. In the third chapter he gives the old
definition of species, that they are fixed and immutable, and then
speaks of the animal series, saying:
"I do not mean by this to say that the existing animals form a very
simple series, and especially evenly graduated; but I claim that
they form a branched series,[180] irregularly graduated, and which
has no discontinuity in its parts, or which, at least, has not
always had, if it is true that, owing to the extinction of some
species, there are some breaks. It follows that the _species_ which
terminates each branch of the general series is connected at least
on one side with other _species_ which intergrade with it" (p. 59).
He then points out the difficulty of determining what are species in
certain large genera, such as Papilio, Ichneumon, etc. How new species
arise is shown by observation.
"A number of facts teaches us that in proportion as the individuals
of one of our species are subjected to changes in situation,
climate, mode of life or habits, they thereby receive influences
which gradually change the consistence and the proportions of their
parts, their form, their faculties, even their structure; so that it
follows that all of them after a time participate in the changes to
which they have been subjected.
"In the same climate very different situations and exposures cause
simple variations in the individuals occurring there; but, after the
lapse of time, the continual differences of situation of the
individuals of which I speak, which live and successively reproduce
under the same circumstances, produce differences in them which
become, in some degree, essential to their existence, so that at the
end of many successive generations these individuals, which
originally belonged to another species, became finally transformed
into a new species distinct from the other.
"For example, should the seeds of a grass or of any other plant
natural to a moist field be carried by any means at first to the
slope of a neighboring hill, where the soil, although more elevated,
will yet be sufficiently moist to allow the plant to live there, and
if it results, after having lived there and having passed through
several generations, that it gradually reaches the dry and almost
arid soil of a mountain side; if the plant succeeds in living there,
and perpetuates itself there during a series of generations, it will
then be so changed that any botanists who should find it there would
make a distinct species of it.
"The same thing happens in the case of animals which circumstances
have forced to change in climate, mode of life, and habits; but in
their case the influences of the causes which I have just cited need
still more time than the plants to bring about notable changes in
the individuals.
"The idea of embracing, under the name of _species_, a collection of
like individuals which are perpetuated by generation, and which have
remained the same as long as nature has endured, implies the
necessity that the individuals of one and the same species should
not cross with individuals of a different species.
"Unfortunately observation has proved, and still proves every day,
that this consideration is unfounded; for hybrids, very common among
plants, and the pairings which we often observe between the
individuals of very different _species_ of animals, have led us to
see that the limits between these supposed constant species are not
so fixed as has been imagined.
"In truth, nothing often results from these singular unions,
especially if they are very ill-assorted, and then the individuals
which do result from them are usually infertile; but also, when the
disparities are less great, we know that the default in question
does not occur.
"But this cause only suffices to create, step by step, varieties
which finally become races, and which, with time, constitute what we
call _species_.
"To decide whether the idea which is formed of the _species_ has any
real foundation, let us return to the considerations which I have
already explained; they lead us to see:
"1. That all the organized bodies of our globe are true productions
of Nature, which she has successively formed after the lapse of much
time;
"2. That, in her course. Nature has begun, and begins over again
every day, to form the simplest organisms, and that she directly
creates only those, namely, which are the first germs (_ébauches_)
of organization, which are designated by the expression of
_spontaneous generations_;
"3. That the first germs of the animal and plant having been formed
in appropriate places and circumstances, the faculties of a
beginning life and of an organic movement established, have
necessarily gradually developed the organs, and that with time they
have diversified them, as also the parts;
"4. That the power of growth in each part of the organized body
being inherent in the first created forms of life, it has given rise
to different modes of multiplication and of regeneration of
individuals; and that consequently the progress acquired in the
composition of the organization and in the shape and diversity of
the parts has been preserved;
"5. That with the aid of sufficient time, of circumstances which
have been necessarily favorable, of changes of condition that every
part of the earth's surface has successively undergone--in a word,
by the power which new situations and new habits have of modifying
the organs of living beings, all those which now exist have been
gradually formed such as we now see them;
"6. Finally, that, according to a similar order of things, living
beings having undergone each of the more or less great changes in
the condition of their structure and parts, that which we call a
_species_ among them has been gradually and successively so formed,
having only a relative constancy in its condition, and not being as
old as Nature herself.
"But, it will be said, when it is supposed that by the aid of much
time and of an infinite variation in circumstances, Nature has
gradually formed the different animals known to us, shall we not be
stopped in this supposition by the simple consideration of the
admirable diversity which we observe in the _instincts_ of different
animals, and by that of the marvels of every kind presented by their
different kinds of _industry_?
"Shall we dare to extend the spirit of system so far as to say that
it is Nature who has herself alone created this astonishing
diversity of means, of contrivances, of skill, of precautions, of
patience, of which the _industry_ of animals offers us so many
examples? What we observe in this respect in the simple class of
_insects_, is it not a thousand times more than sufficient to make
us realize that the limit to the power of Nature in nowise permits
her to herself produce so many marvels, but to force the most
obstinate philosopher to recognize that here the will of the Supreme
Author of all things has been necessary, and has alone sufficed to
create so many admirable things?
"Without doubt, one would be rash or, rather, wholly insensate, to
pretend to assign limits to the power of the first Author of all
things; but, aside from that, no one could dare to say that this
infinite power could not will that which Nature even shows us it has
willed"[181] (p. 67).
Referring to the alleged proof of the fixity of species brought forward
by Cuvier in the _Annales du Muséum d'Histoire naturelle_ (i., pp. 235
and 236) that the mummied birds, crocodiles, and other animals of Egypt
present no differences from those now living, Lamarck says:
"It would assuredly be very singular if it were otherwise, because
the position of Egypt and its climate are still almost exactly what
they were at that epoch. Moreover, the birds which live there still
exist under the same circumstances as they were then, not having
been obliged to change their habits.
"Moreover, who does not perceive that birds, which can so easily
change their situation and seek places which suit them are less
subject than many other animals to the variations of local
circumstances, and hence less restricted in their habits."
He adds the fact that the animals in question have inhabited Egypt for
two or three thousand years, and not necessarily from all time, and that
this is not time enough for marked changes. He then gives the following
definition of species, which is the best ever offered: "Species, then,
have only a relative stability, and are invariable only temporarily."
"Yet, to facilitate the study and knowledge of so many different
organisms it is useful to give the name of _species_ to every
similar collection of similar individuals which are perpetuated by
heredity (_génération_) in the same condition, so long as the
circumstances of their situation do not change enough to render
variable their habits, character, and form."
He then discusses fossil species in the way already described in
Chapter III. (p. 75).
The subject of the checks upon over-population by the smaller and weaker
animals, or the struggle for existence, is thus discussed in
Chapter IV.:
"Owing to the extreme multiplication of the small species, and
especially of the most imperfect animals, the multiplicity of
individuals might be prejudicial to the preservation of the species,
to that of the progress acquired in the improvement of the
organization--in a word, to the general order, if nature had not
taken precautions to keep this multiplication within due limits over
which she would never pass.
"Animals devour one another, except those which live only on plants;
but the latter are exposed to being devoured by the carnivorous
animals.
"We know that it is the strongest and the best armed which devour
the weaker, and that the larger kinds devour the smaller.
Nevertheless, the individuals of a single species rarely devour each
other: they war upon other races.[182]
"The multiplication of the small species of animals is so
considerable, and the renewals of their generations are so prompt,
that these small species would render the earth uninhabitable to the
others if nature had not set a limit to their prodigious
multiplication. But since they serve as prey for a multitude of
other animals, as the length of their life is very limited, and as
the lowering of the temperature kills them, their numbers are always
maintained in proper proportions for the preservation of their races
and that of others.
"As to the larger and stronger animals, they would be too dominant
and injure the preservation of other races if they should multiply
in too great proportions. But their races devouring each other, they
would only multiply slowly and in a small number at a time; this
would maintain in this respect the kind of equilibrium which should
exist.
"Finally, only man, considered separately from all which is
characteristic of him, seems capable of multiplying indefinitely,
because his intelligence and his resources secure him from seeing
his increase arrested by the voracity of any animals. He exercises
over them such a supremacy that, instead of fearing the larger and
stronger races of animals, he is thus rather capable of destroying
them, and he continually checks their increase.
"But nature has given him numerous passions, which, unfortunately,
developing with his intelligence, thus place a great obstacle to
the extreme multiplication of the individuals of his species.
"Indeed, it seems as if man had taken it upon himself unceasingly to
reduce the number of his fellow-creatures; for never, I do not
hesitate to say, will the earth be covered with the population that
it could maintain. Several of its habitable parts would always be
alternately very sparsely populated, although the time for these
alternate changes would be to us measureless.
"Thus by these wise precautions everything is preserved in the
established order; the changes and perpetual renewals which are
observable in this order are maintained within limits over which
they cannot pass; the races of living beings all subsist in spite of
their variations; the progress acquired in the improvement of the
organization is not lost; everything which appears to be disordered,
overturned, anomalous, reënters unceasingly into the general order,
and even coöperates with it; and especially and always the will of
the sublime Author of nature and of all existing things is
invariably executed" (pp. 98-101).
In the sixth chapter the author treats of the degradation and
simplification of the structure from one end to the other of the animal
series, proceeding, as he says, inversely to the general order of
nature, from the compound to the more simple. Why he thus works out this
idea of a general degradation is not very apparent, since it is out of
tune with his views, so often elsewhere expressed, of a progressive
evolution from the simple to the complex, and to his own classification
of the animal kingdom, beginning as it does with the simplest forms and
ending with man. Perhaps, however, he temporarily adopts the prevailing
method of beginning with the highest forms in order to bring out
clearly the successive steps in inferiority or degradation presented in
descending the animal scale.
We will glean some passages of this chapter which bear on his theory of
descent. Speaking of the different kinds of aquatic surroundings he
remarks:
"In the first place it should be observed that in the waters
themselves she [Nature] presents considerably diversified
circumstances; the fresh waters, marine waters, calm or stagnant
waters, running waters or streams, the waters of warm climates,
those of cold regions, finally those which are shallow and those
which are very deep, offer many special circumstances, each of which
acts differently on the animals living in them. Now, in a degree
equal to the make-up of the organization, the races of animals which
are exposed to either of these circumstances have been submitted to
special influences and have been diversified by them."
He then, after referring to the general degradation of the Batrachians,
touches upon the atrophy of legs which has taken place in the snakes:
"If we should consider as a result of _degradation_ the loss of legs
seen in the snakes, the _Ophidia_ should be regarded as constituting
the lowest order of reptiles; but it would be an error to admit this
consideration. Indeed, the serpents being animals which, in order to
hide themselves, have adopted the habit of gliding directly along
the ground, their body has lengthened very considerably and
disproportionately to its thickness. Now, elongated legs proving
disadvantageous to their necessity of gliding and hiding, very short
legs, being only four in number, since they are vertebrate animals,
would be incapable of moving their bodies. Thus the habits of these
animals have been the cause of the disappearance of their legs, and
yet the _batrachians_, which have them, offer a more degraded
organization, and are nearer the fishes" (p. 155).
Referring on the next page to the fishes, he remarks:--
"Without doubt their general form, their lack of a constriction
between the head and the body to form a neck, and the different fins
which support them in place of legs, are the results of the
influence of the dense medium which they inhabit, and not that of
the _dégradation_ of their organization. But this modification
(_dégradation_) is not less real and very great, as we can convince
ourselves by examining their internal organs; it is such as to
compel us to assign to the fishes a rank lower than that of the
reptiles."
He then states that the series from the lamprey and fishes to the
mammals is not a regularly gradated one, and accounts for this "because
the work of nature has been often changed, hindered, and diverted in
direction by the influences which singularly different, even contrasted,
circumstances have exercised on the animals which are there found
exposed in the course of a long series of their renewed generations."
Lamarck thus accounts for the production of the radial symmetry of the
medusæ and echinoderms, his _Radiaires_. At the present day this
symmetry is attributed perhaps more correctly to their more or less
fixed mode of life.
"It is without doubt by the result of this means which nature
employs, at first with a feeble energy with _polyps_, and then with
greater developments in the _Radiata_, that the radial form has been
acquired; because the subtile ambient fluids, penetrating by the
alimentary canal, and being expansive, have been able, by an
incessantly renewed repulsion from the centre towards every point of
the circumference, to give rise to this radiated arrangement of
parts.
"It is by this cause that, in the Radiata, the intestinal canal,
although still very imperfect, since more often it has only a single
opening, is yet complicated with numerous radiating vasculiform,
often ramified, appendages.
"It is, doubtless, also by this cause that in the soft Radiates, as
the medusæ, etc., we observe a constant isochronic movement,
movement very probably resulting from the successive intermissions
between the masses of subtile fluids which penetrate into the
interior of these animals and those of the same fluids which escape
from it, often being spread throughout all their parts.
"We cannot say that the isochronic movements of the soft Radiates
are the result of their respiration; for below the vertebrate
animals nature does not offer, in that of any animal, these
alternate and measured movements of inspiration and expiration.
Whatever may be the respiration of Radiates, it is extremely slow,
and is executed without perceptible movements" (p. 200).
_The Influence of Circumstances on the Actions and Habits of Animals._
It is in Chapter VII. that the views of Lamarck are more fully presented
than elsewhere, and we therefore translate all of it as literally as
possible, so as to preserve the exact sense of the author.
"We do not here have to do with a line of argument, but with the
examination of a positive fact, which is more general than is
supposed, and which has not received the attention it deserves,
doubtless because, very often, it is quite difficult to discover.
This fact consists in the influence which circumstances exert on the
different organisms subjected to them.
"In truth, for a long time there has been noticed the influence of
different states of our organization on our character, our
propensities (_penchants_), our actions, and even our ideas; but it
seems to me that no one has yet recognized that of our actions and
of our habits on our organization itself. Now, as these actions and
these habits entirely depend on the circumstances in which we
habitually find ourselves, I shall try to show how great is the
influence which these circumstances exercise on the general form, on
the condition of the parts, and even on the organization of living
bodies. It is therefore this very positive fact which is to be the
subject of this chapter.
"If we have not had numerous occasions to plainly recognize the
effects of this influence on certain organisms which we have
transported under entirely new and different circumstances, and if
we had not seen these effects and the changes resulting from them
produced, in a way, under our very eyes, the important fact in
question would have always remained unknown.
"The influence of circumstances is really continuously and
everywhere active on living beings, but what renders it difficult
for us to appreciate this influence is that its effects only become
sensible or recognizable (especially in the animals) at the end of a
long period.
"Before stating and examining the proofs of this fact, which
deserves our attention, and which is very important for a zoölogical
philosophy, let us resume the thread of the considerations we had
begun to discuss.
"In the preceding paragraph we have seen that it is now an
incontrovertible fact that, in considering the animal scale in a
sense the inverse of that of nature, we find that there exists in
the groups composing this scale a continuous but irregular
modification (_dégradation_) in the organization of animals which
they comprise, an increasing simplification in the organization of
these organisms; finally, a proportionate diminution in the number
of faculties of these beings.
"This fact once recognized may throw the greatest light on the very
order which nature has followed in the production of all the
existing animals; but it does not show why the structure of animals
in its increasing complexity from the more imperfect up to the most
perfect offers only an irregular gradation, whose extent presents a
number of anomalies or digressions which have no appearance of order
in their diversity.
"Now, in seeking for the reason of this singular irregularity in the
increasing complexity of organization of animals, if we should
consider the outcome of the influences that the infinitely
diversified circumstances in all parts of the globe exercise on the
general form, the parts, and the very organization of these animals,
everything will be clearly explained.
"It will, indeed, be evident that the condition in which we find all
animals is, on one side, the result of the increasing complexity of
the organization which tends to form a regular gradation, and, on
the other, that it is that of the influences of a multitude of very
different circumstances which continually tend to destroy the
regularity in the gradations of the increasing complexity of the
organization.
"Here it becomes necessary for me to explain the meaning I attach to
the expression _circumstances influencing the form and structure of
animals_--namely, that in becoming very different they change, with
time, both their form and organization by proportionate
modifications.
"Assuredly, if these expressions should be taken literally, I should
be accused of an error; for whatever may be the circumstances, they
do not directly cause any modification in the form and structure of
animals.
"But the great changes in the circumstances bring about in animals
great changes in their needs, and such changes in their needs
necessarily cause changes in their actions. Now, if the new needs
become constant or very permanent, the animals then assume new
_habits_, which are as durable as the needs which gave origin to
them. We see that this is easily demonstrated and even does not need
any explanation to make it clearer.
"It is then evident that a great change in circumstances having
become constant in a race of animals leads these animals into new
habits.
"Now, if new circumstances, having become permanent in a race of
animals, have given to these animals new _habits_--that is to say,
have led them to perform new actions which have become
habitual--there will from this result the use of such a part by
preference to that of another, and in certain cases the total lack
of use of any part which has become useless.
"Nothing of all this should be considered as a hypothesis or as a
mere peculiar opinion; they are, on the contrary, truths which
require, in order to be made evident, only attention to and the
observation of facts.
"We shall see presently by the citation of known facts which prove
it, on one side that the new wants, having rendered such a part
necessary, have really by the result of efforts given origin to this
part, and that as the result of its sustained use it has gradually
strengthened it, developed, and has ended in considerably increasing
its size; on the other side we shall see that, in certain cases, the
new circumstances and new wants having rendered such a part wholly
useless, the total lack of use of this part has led to the result
that it has gradually ceased to receive the development which the
other parts of the animal obtain; that it gradually becomes
emaciated and thin; and that finally, when this lack of use has been
total during a long time, the part in question ends in disappearing.
All this is a positive fact; I propose to give the most convincing
proofs.
"In the plants, where there are no movements, and, consequently, no
habits properly so called, great changes in circumstances do not
bring about less great differences in the development of their
parts; so that these differences originate and develop certain of
them, while they reduce and cause several others to disappear. But
here everything operates by the changes occurring in the nutrition
of the plant, in its absorptions and transpirations, in the amount
of heat, light, air, and humidity which it habitually receives;
finally, in the superiority that certain of the different vital
movements may assume over others.
"Between individuals of the same species, some of which are
constantly well nourished, and in circumstances favorable to their
entire development, while the others live under reversed
circumstances, there is brought about a difference in the condition
of these individuals which gradually becomes very remarkable. How
many examples could I not cite regarding animals and plants, which
would confirm the grounds for this view! Now, if the circumstances
remain the same, rendering habitual and constant the condition of
individuals badly fed, diseased, or languishing, their internal
organization becomes finally modified, and reproduction between the
individuals in question preserves the acquired modifications, and
ends in giving rise to a race very distinct from that of the
individuals which unceasingly meet with circumstances favorable to
their development.
"A very dry spring-time is the cause of the grass of a field growing
very slowly, remaining scraggy and puny, flowering and fruiting
without growing much.
"A spring interspersed with warm days and rainy days makes the same
grass grow rapidly, and the harvest of hay is then excellent.
"But if any cause perpetuates the unfavorable circumstances
surrounding these plants, they vary proportionally, at first in
their appearance and general condition, and finally in several
particulars of their characters.
"For example, if some seed of any of the grasses referred to should
be carried into an elevated place, on a dry and stony greensward
much exposed to the winds, and should germinate there, the plant
which should be able to live in this place would always be badly
nourished, and the individuals reproduced there continuing to exist
under these depressing circumstances, there would result a race
truly different from that living in the field, though originating
from it. The individuals of this new race would be small, scraggy,
and some of their organs, having developed more than others, would
then offer special proportions.
"Those who have observed much, and who have consulted the great
collections, have become convinced that in proportion as the
circumstances of habitat, exposure, climate, food, mode of life,
etc., come to change, the characters of size, form, proportion
between the parts, color, consistence, agility, and industry in the
animals change proportionally.
"What nature accomplishes after a long time, we bring about every
day by suddenly changing, in the case of a living plant, the
circumstances under which it and all the individuals of its species
exist.
"All botanists know that the plants which they transplant from their
birthplace into gardens for cultivation gradually undergo changes
which at last render them unrecognizable. Many plants naturally
very hairy then become glabrous, or almost so; many of those which
were creeping and trailing, then become erect; others lose their
spines or their prickles; others still, from the woody and perennial
condition which their stem possesses in a warm climate, pass, in our
climate, into an herbaceous condition, and among these several are
nothing more than annual plants; finally, the dimensions of their
parts themselves undergo very considerable changes. These effects of
changes of circumstances are so well known that botanists prefer not
to describe garden plants, at least only those which have been newly
cultivated.
"Is not cultivated wheat (_Triticum sativum_) only a plant brought
by man into the condition in which we actually see it? Who can tell
me in what country such a plant lives in a state of nature--that is
to say, without being there the result of its culture in some
neighboring region?
"Where occur in nature our cabbage, lettuce, etc., in the condition
in which we see them in our kitchen-gardens? Is it not the same as
regards a number of animals which domestication has changed or
considerably modified?
"What very different races among our fowls and domestic pigeons,
which we have obtained by raising them in different circumstances
and in different countries, and how vainly do we now endeavor to
rediscover them in nature!
"Those which are the least changed, without doubt by a more recent
process of domestication, and because they do not live in a climate
which is foreign to them, do not the less possess, in the condition
of some of their parts, great differences produced by the habits
which we have made them contract. Thus our ducks and our domestic
geese trace back their type to the wild ducks and geese; but ours
have lost the power of rising into the high regions of the air, and
of flying over extensive regions; finally, a decided change has
been wrought in the state of their parts compared with that of
animals of the race from which they have descended.
"Who does not know that such a native bird, which we raise in a cage
and which lives there five or six years in succession, and after
that replaced in nature--namely, set free--is then unable to fly
like its fellows which have always been free? The slight change of
circumstance operating on this individual has only diminished its
power of flight, and doubtless has not produced any change in the
shape of its parts. But if a numerous series of generations of
individuals of the same race should have been kept in captivity for
a considerable time, there is no doubt but that even the form of the
parts of these individuals would gradually undergo notable changes.
For a much stronger reason, if, instead of a simple captivity
constantly maintained over them, this circumstance had been at the
same time accompanied by a change to a very different climate, and
if these individuals by degrees had been habituated to other kinds
of food, and to other kinds of movements to obtain it; certainly
these circumstances, united and becoming constant, would insensibly
form a new and special race.
"Where do we find, in nature, this multitude of races of _dogs_,
which, as the result of domesticity to which we have reduced these
animals, have been brought into their present condition? Where do we
find these bull-dogs, greyhounds, water spaniels, spaniels,
pug-dogs, etc., etc., races which present among themselves much
greater differences than those which we admit to be specific in wild
animals of the same genus?
"Without doubt, a primitive single race, very near the wolf, if it
is not itself the true type, has been submitted by man, at some
period, to the process of domestication. This race, which then
offered no difference between its individuals, has been gradually
dispersed by man into different countries, with different climates;
and after a time these same individuals, having undergone the
influences of their habitats, and of the different habits they were
obliged to contract in each country, have undergone remarkable
changes, and have formed different special races. Now, the man who,
for commercial reasons or from interests of any other kind, travels
a very great distance, having carried into a densely populated
place, as for example a great capital, different races of dogs
originated in some very distant country, then the increase of these
races by heredity (_génération_) has given rise successively to all
those we now know.
"The following fact proves, as regards plants, how a change in any
important circumstance leads to a change in the parts of their
organisms.
"So long as _Ranunculus aquatilis_ is submerged in the water, its
leaves are all finely incised and the divisions hair-like; but when
the stalks of this plant reach the surface of the water, the leaves
which grow out in the air are wider, rounded, and simply lobed. If
some feet from the same plant the roots succeed in pushing into a
soil only damp, without being submerged, their stalks then are
short, none of their leaves are divided into capillary divisions,
which gives rise to _Ranunculus hederaceus_, which the botanists
regard as a species whenever they meet with it.
"There is no doubt that as regards animals important changes in the
circumstances under which they are accustomed to live do not produce
alteration in their organs; for here the changes are much slower in
operating than in plants, and, consequently, are to us less marked,
and their cause less recognizable.
"As to the circumstances which have so much power in modifying the
organs of living beings, the most influential are, doubtless, the
diversity of the surroundings in which they live; but besides this
there are many others which, in addition, have a considerable
influence in the production of the effects in question.
"It is known that different localities change in nature and quality
owing to their position, their nature, and their climate, as is
easily seen in passing over different places distinguished by
special features; hence we see a cause of variation for the animals
and plants which live in these different places. But what we do not
sufficiently know, and even what we generally refuse to believe, is
that each place itself changes with time in exposure, in climate, in
nature, and quality, although with a slowness so great in relation
to our own continuance that we attribute to it a perfect stability.
"Now, in either case, these changed localities proportionally change
the circumstances relative to the organisms which inhabit them, and
the latter then give rise to other influences bearing on these same
beings.
"We perceive from this that, if there are extremes in these changes,
there are also gradations--namely, degrees which are intermediate
and which fill the interval. Consequently there are also gradations
in the differences which distinguish what we call _species_.
"It is then evident that the whole surface of the earth offers, in
the nature and situation of the matters which occupy its different
points, a diversity of circumstances which is throughout in relation
with that of the forms and parts of animals, independent of the
special diversity which necessarily results from the progress of the
composition of organization in each animal.
"In each locality where animals can live, the circumstances which
establish there an order of things remain for a long time the same,
and really change there only with a slowness so great that man
cannot directly notice them. He is obliged to consult monuments to
recognize that in each one of these places the order of things that
he discovers there has not always been the same, and to perceive
that it will change more.
"The races of animals which live in each of these places should,
then, retain their customary habits there also for a long time;
hence to us seems an apparent constancy of races which we call
_species_--constancy which has originated among us the idea that
these races are as ancient as nature.
"But in the different points of the earth's surface which can be
inhabited, nature and the situation of the places and climates
constitute there, for the animals as for the plants, _different
circumstances_ of all sorts of degrees. The animals which inhabit
these different places should then differ from each other, not only
on account of the state of nature of the organization in each race,
but, besides, by reason of the habits that the individuals of each
race there are forced to have; so, in proportion as he traverses the
larger parts of the earth's surface the observing naturalist sees
circumstances changing in a manner somewhat noticeable; he
constantly sees that the species change proportionately in their
characters.
"Now, the true order of things necessary to consider in all this
consists in recognizing:
"1. That every slight change maintained under the circumstances
where occur each race of animals, brings about in them a real change
in their wants.
"2. That every change in the wants of animals necessitates in them
other movements (_actions_) to satisfy the new needs, and
consequently other habits.
"3. That every new want necessitating new actions to satisfy it,
demands of the animal which feels it both the more frequent use of
such of its parts of which before it made less use, which develops
and considerably enlarges them, and the use of new parts which
necessity has caused to insensibly develop in it by the effects of
its inner feelings; which I shall constantly prove by known facts.
"Thus, to arrive at a knowledge of the true causes of so many
different forms and so many different habits of which the known
animals offer us examples, it is necessary to consider that
circumstances infinitely diversified, but all slowly changing, into
which the animals of each race are successively thrown, have caused,
for each of them, new wants and necessarily changes in their habits.
Moreover, this truth, which cannot be denied, being once recognized,
it will be easy to see how the new needs have been able to be
satisfied, and the new habits formed, if any attention be given to
the two following laws of nature, which observation always confirms:
"_First Law._
"In every animal which has not exceeded the term of its development,
the more frequent and sustained use of any organ gradually
strengthens this organ, develops and enlarges it, and gives it a
strength proportioned to the length of time of such use; while the
constant lack of use of such an organ imperceptibly weakens it,
causes it to become reduced, progressively diminishes its faculties,
and ends in its disappearance.
"_Second Law._
"Everything which nature has caused individuals to acquire or lose
by the influence of the circumstances to which their race may be for
a long time exposed, and consequently by the influence of the
predominant use of such an organ, or by that of the constant lack of
use of such part, it preserves by heredity (_génération_) and passes
on to the new individuals which descend from it, provided that the
changes thus acquired are common to both sexes, or to those which
have given origin to these new individuals.
"These are the two fundamental truths which can be misunderstood
only by those who have never observed or followed nature in its
operations, or only by those who allow themselves to fall into the
error which I have combated.
"Naturalists having observed that the forms of the parts of animals
compared with the uses of these parts are always in perfect accord,
have thought that the forms and conditions of parts have caused the
function; but this is a mistake, for it is easy to demonstrate by
observation that it is, on the contrary, the needs and uses of
organs which have developed these same parts, which have even given
origin to them where they did not exist, and which consequently have
given rise to the condition in which we observe them in each animal.
"If this were not so, it would have been necessary for nature to
have created for the parts of animals as many forms as the diversity
of circumstances in which they have to live had required, and that
these forms and also the circumstances had never varied.
"This is certainly not the existing order of things, and if it were
really such, we should not have the race-horses of England; we
should not have our great draft horses, so clumsy and so different
from the first named, for nature herself has not produced their
like; we should not, for the same reason, have terrier dogs with bow
legs, greyhounds so swift in running, water-spaniels, etc.; we
should not have tailless fowls, fantail pigeons, etc.; finally, we
could cultivate the wild plants as much as we pleased in the rich
and fertile soil of our gardens without fearing to see them change
by long culture.
"For a long time we have felt the force of the saying which has
passed into the well-known proverb--_habits form a second nature_.
"Assuredly, if the habits and nature of each animal can never vary,
the proverb is false, has no foundation, and does not apply to the
instances which led to its being spoken.
"If we should seriously consider all that I have just stated, it
might be thought that I had good reason when in my work entitled
_Recherches sur les Corps vivans_ (p. 50) I established the
following proposition:
"'It is not the organs--that is to say, the nature and form of the
parts of the body of an animal--which have given rise to its habits
and its special faculties; but it is, on the contrary, its habits,
its manner of life, and the circumstances in which are placed the
individuals from which it originates, which have, with time, brought
about the form of its body, the number and condition of its organs,
finally, the faculties which it enjoys.'
"If we weigh this proposition, and if we recall all the observations
which nature and the state of things continually lead us to do, then
its importance and its solidity will become more evident.
"Time and favorable circumstances are, as I have already said, the
two principal means which nature employs to give existence to all
her productions: we know that time for her has no limits, and that
consequently it is ever at her disposal.
"As to the circumstances of which she has need, and which she uses
still daily to cause variations in all that she continues to
produce, we can say that they are, in some degree, for her
inexhaustible.
"The principal circumstances arise from the influence of climate;
from those of different temperatures of the atmosphere, and from all
the environing media; from that of the diversity of different
localities and their situation; from that of habits, the ordinary
movements, the most frequent actions; finally, from that of means of
preservation, of mode of living, of defence, of reproduction, etc.
"Moreover, owing to these diverse influences, the faculties increase
and become stronger by use, become differentiated by the new habits
preserved for long ages, and insensibly the organization, the
consistence--in a word, the nature and condition of parts, as also
of the organs--participate in the results of all these influences,
become preserved, and are propagated by generation.
"These truths, which are only the results of the two natural laws
above stated, are in every case completely confirmed by facts; they
clearly indicate the course of nature in all the diversity of its
products.
"But instead of contenting ourselves with generalities which might
be considered as hypothetical, let us directly examine the facts,
and consider, in the animals, the result of the use or disuse of
their organs on the organs themselves, according to the habits that
each race has been compelled to contract.
"I shall now attempt to prove that the constant lack of exercise of
organs at first diminishes their faculties, gradually impoverishes
them, and ends by making them disappear, or even causing them to be
atrophied, if this lack of use is perpetuated for a very long time
through successive generations of animals of the same race.
"I shall next prove that, on the contrary, the habit of exercising
an organ, in every animal which has not attained the limit of the
diminution of its faculties, not only perfects and increases the
faculties of this organ, but, besides, enables it to acquire
developments and dimensions which insensibly change it; so that with
time it renders it very different from the same organ in another
animal which exercises it much less.
"_The lack of use of an organ, become constant by the habits formed,
gradually impoverishes this organ, and ends by causing it to
disappear and even to destroy it._
"As such a proposition can only be admitted on proof, and not by its
simple announcement, let us prove it by the citation of the leading
known facts on which it is based.
"The vertebrate animals, whose plan of organization is in all nearly
the same, although they offer much diversity in their parts, have
jaws armed with _teeth_; moreover, those among them which
circumstances have placed in the habit of swallowing their food
without previous _mastication_ are exposed to the result that their
teeth become undeveloped. These teeth, then, either remain concealed
between the bony edges of the jaws, without appearing above, or even
their gums are found to have been atrophied.
"In the baleen whales, which have been supposed to be completely
deprived of teeth, M. Geoffroy has found them concealed in the jaws
of the _foetus_ of this animal. This professor has also found in
the birds the groove where the teeth should be situated; but they
are no longer to be seen there.
"In the class even of mammals, which comprises the most perfect
animals, and chiefly those in which the vertebrate plan of
organization is most perfectly carried out, not only the baleen has
no usable teeth, but the ant-eater (_Myrmecophaga_) is also in the
same condition, whose habit of not masticating its food has been for
a long time established and preserved in its race.
"The presence of eyes in the head is a characteristic of a great
number of different animals, and becomes an essential part of the
plan of organization of vertebrates.
"Nevertheless the mole, which owing to its habits makes very little
use of vision, has only very small eyes, which are scarcely visible,
since they exercise these organs to a very slight extent.
"The _Aspalax_ of Olivier (_Voyage en Egypte et en Perse_, ii.
pl. 28 f. 2), which lives under ground like the mole, and which
probably exposes itself still less than that animal to the light of
day, has totally lost the power of sight; also it possesses only
vestiges of the organ of which it is the seat; and yet these
vestiges are wholly concealed under the skin and other parts which
cover them, and do not permit the least access to the light.
"The _Proteus_, an aquatic reptile allied to the salamander in its
structure, and which lives in the dark subterranean waters of deep
caves, has, like the _Aspalax_, only vestiges of the organs of
sight--vestiges which are covered and concealed in the same manner.
"We turn to a decisive consideration relative to this question.
"Light does not penetrate everywhere; consequently animals which
habitually live in situations where it does not penetrate lack the
occasion of exercising the organs of sight, if nature has provided
them with them. Moreover, the animals which make part of the plan of
organization in which _eyes_ are necessarily present, have
originally had them. However, since we find them among those which
are deprived of the use of this organ, and which have only vestiges
concealed and covered over, it should be evident that the
impoverishment and even the disappearance of these organs are the
result of a constant lack of exercise.
"What proves it is that the organ of _hearing_ is never in this
condition, and that we always find it in the animals when the nature
of their organization should require its existence; the reason is as
follows.
"The _cause of sound_, that which, moved by the shock or the
vibrations of bodies, transmits to the organ of hearing the
impression which it receives, penetrates everywhere, traverses all
the media, and even the mass of the densest bodies: from this it
results that every animal which makes a part of a plan of
organization to which _hearing_ is essential, has always occasion to
exercise this organ in whatever situation it lives. So, among the
_vertebrate animals_ we see none deprived of their organs of
hearing; but in the groups below them, when the same organs are once
wanting, we do not again find them.
"It is not so with the organ of sight, for we see this organ
disappear, reappear, and again disappear, in proportion to the
possibility or impossibility of the animal's exercising it.
"In the _acephalous molluscs_, the great development of the mantle
of these molluscs has rendered their eyes and even their head
entirely useless. These organs, also forming a part of a plan of
organization which should comprise them, have disappeared and
atrophied from constant lack of use.
"Finally, it is a part of the plan of organization of _reptiles_, as
in other vertebrate animals, to have four legs appended to their
skeleton. The serpents should consequently have four, though they do
not form the lowest order of reptiles, and are not so near the
fishes as the batrachians (the frogs, the salamanders, etc.).
"However, the serpents having taken up the habit of gliding along
the ground, and of concealing themselves in the grass, their body,
owing to continually repeated efforts to elongate itself so as to
pass through narrow spaces, has acquired a considerable length
disproportionate to its size. Moreover, limbs would have been very
useless to these animals, and consequently would not have been
employed: because long legs would have interfered with their need of
gliding, and very short legs, not being more than four in number,
would have been incapable of moving their body. Hence the lack of
use of these parts having been constant in the races of these
animals, has caused the total disappearance of these same parts,
although really included in the plan of organization of the animals
of their class.
"Many insects which by the natural character of their order, and
even of their genus, should have wings, lack them more or less
completely from disuse. A quantity of Coleoptera, Orthoptera,
Hymenoptera, and of Hemiptera, etc., afford examples; the habits of
these animals do not require them to make use of their wings.
"But it is not sufficient to give the explanation of the cause which
has brought about the condition of the organs of different
animals--a condition which we see to be always the same in those of
the same species; we must besides observe the changes of condition
produced in the organs of one and the same individual during its
life, by the single result of a great change in the special habits
in the individuals of its species. The following fact, which is one
of the most remarkable, will serve to prove the influence of habits
on the condition of organs, and show how changes wrought in the
habits of an individual, produce the condition of the organs which
are brought into action during the exercise of these habits.
"M. Tenon, member of the Institute, has given an account to the
Class of Sciences, that having examined the intestinal canal of
several men who had been hard drinkers all their lives, he had
constantly found it to be shortened to an extraordinary extent,
compared with the same organ in those not given to such a habit.
"We know that hard drinkers, or those who are addicted to
drunkenness, take very little solid food, that they eat very
lightly, and that the beverage which they take in excess frequently
suffices to nourish them.
"Moreover, as fluid aliments, especially spirituous liquors, do not
remain a long time either in the stomach or in the intestines, the
stomach and the remainder of the intestinal canal lose the habit of
being distended in intemperate persons, so also in sedentary persons
and those engaged in mental labor, who are habituated to take but
little food. Gradually and at length their stomach becomes
contracted, and their intestines shortened.
"We are not concerned here with the shrinkage and shortening
produced by a puckering of the parts, which permit ordinary
extension, if instead of a continued emptiness these viscera should
be filled; the shrinkage and shortening in question are real,
considerable, and such that these organs would burst open rather
than yield suddenly to the causes which would require ordinary
extension.
"In circumstances of persons of the same age, compare a man who, in
order to devote himself to habitual study and mental work, which
have rendered his digestion more difficult, has contracted the habit
of eating lightly, with another who habitually takes a good deal of
exercise, walks out often, and eats heartily; the stomach of the
first will be weakened, and a small quantity of food will fill it,
while that of the second will be not only maintained in its ordinary
health but even strengthened.
"We have here the case of an organ much modified in its dimensions
and in its faculties by the single cause of a change in habits
during the life of the individual.
"_The frequent use of an organ become constant by habit increases
the faculties of this organ, even develops it, and enables it to
acquire dimensions and a power of action which it does not possess
in animals which exercise less._
"We have just said that the lack of employment of an organ which
necessarily exists modifies it, impoverishes it, and ends by its
disappearing entirely.
"I shall now demonstrate that the continued employment of an organ,
with the efforts made to draw out its powers under circumstances
where it would be of service, strengthens, extends, and enlarges
this organ, or creates a new one which can exercise the necessary
functions.
"The bird which necessity drives to the water to find there prey
fitted for its sustenance, opens the digits of its feet when it
wishes to strike the water and propel itself along its surface. The
skin which unites these digits at their base, by these acts of
spreading apart being unceasingly repeated contracts the habit of
extending; so that after a while the broad membranes which connect
the digits of ducks, geese, etc., are formed as we see them. The
same efforts made in swimming--_i.e._, in pushing back the water, in
order to advance and to move in this liquid--have likewise extended
the membrane situated between the digits of the frogs, the
sea-turtles, the otter, beaver, etc.
"On the contrary, the bird whose mode of life habituates it to perch
on trees, and which is born of individuals who have all contracted
this habit, has necessarily the digits of the feet longer and shaped
in another way than those of the aquatic animals which I have just
mentioned. Its claws, after a while, became elongated, pointed, and
curved or hook-like in order to grasp the branches on which the
animal often rests.
"Likewise we see that the shore bird, which is not inclined to swim,
and which moreover has need of approaching the edge of the water to
find there its prey, is in continual danger of sinking in the mud.
Now, this bird, wishing to act so that its body shall not fall into
the water, makes every effort to extend and elongate its legs. It
results from this that the long-continued habit that this bird and
the others of its race contract, of extending and continually
elongating their legs, is the _cause_ of the individuals of this
race being raised as if on stilts, having gradually acquired long,
naked legs, which are denuded of feathers up to the thighs and often
above them (_Système des Animaux sans Vertèbres_, p. 16).
"We also perceive that the same bird, wishing to catch fish without
wetting its body, is obliged to make continual efforts to lengthen
its neck. Now, the results of these habitual efforts in this
individual and in those of its race have enabled them, after a
time, to singularly elongate them--as, indeed, is proved by the long
neck of all shore birds.
"If any swimming birds, such as the swan and the goose, whose legs
are short, nevertheless have a very long neck, it is because these
birds in swimming on the surface of the water have the habit of
plunging their head down as far as they can, to catch aquatic larvæ
and different animalcules for food, and because they make no effort
to lengthen their legs.
"When an animal to satisfy its wants makes repeated efforts to
elongate its tongue, it will acquire a considerable length (the
ant-eater, green wood-pecker); when it is obliged to seize anything
with this same organ, then its tongue will divide and become forked.
That of the humming-birds, which seize with their tongue, and that
of the lizard and serpents, which use it to feel and examine objects
in front of them, are proofs of what I advocate.
"Wants, always occasioned by circumstances, and followed by
sustained efforts to satisfy them, are not limited in results, in
modifying--that is to say, in increasing or diminishing--the extent
and the faculties of organs; but they also come to displace these
same organs when certain of these wants become a necessity.
"The fishes which habitually swim in large bodies of water, having
need of seeing laterally, have, in fact, their eyes placed on the
sides of the head. Their bodies, more or less flattened according to
the _species_, have their sides perpendicular to the plane of the
water, and their eyes are placed in such a way that there is an eye
on each flattened side. But those fishes whose habits place them
under the necessity of constantly approaching the shores, and
especially the shelving banks or where the slope is slight, have
been forced to swim on their flattened faces, so as to be able to
approach nearer the edge of the water. In this situation, receiving
more light from above than from beneath, and having a special need
of being always attentive to what is going on above them, this need
has forced one of their eyes to undergo a kind of displacement, and
to assume the very singular situation which is familiar to us in the
_soles_, _turbots_, _dabs_, etc. (_Pleuronectes_ and _Achirus_). The
situation of these eyes is asymmetrical, because this results from
an incomplete change. Now, this change is entirely completed in the
rays, where the transverse flattening of the body is entirely
horizontal, as also the head. Also the eyes of the rays, both
situated on the upper side, have become symmetrical.
"The serpents which glide along the surface of the ground are
obliged chiefly to see elevated objects, or what are above their
eyes. This necessity has brought an influence to bear on the
situation of the organs of vision in these animals; and, in fact,
they have the eyes placed in the lateral and upper parts of the
head, so as to easily perceive what is above or at their sides; but
they only see for a short distance what is in front of them.
Moreover, forced to supply the lack of ability to see and recognize
what is in front of their head, and which might injure them, they
need only to feel such objects with the aid of their tongue, which
they are obliged to dart out with all their power. This habit has
not only contributed to render the tongue slender, very long and
retractile, but has also led in a great number of species to its
division, so as to enable them to feel several objects at once; it
has likewise allowed them to form an opening at the end of their
head, to enable the tongue to dart out without their being obliged
to open their jaws.
"Nothing is more remarkable than the result of habits in the
herbivorous mammals.
"The quadruped to whom circumstances and the wants which they have
created have given for a long period, as also to others of its race,
the habit of browsing on grass, only walks on the ground, and is
obliged to rest there on its four feet the greater part of its life,
moving about very little, or only to a moderate extent. The
considerable time which this sort of creature is obliged to spend
each day to fill itself with the only kind of food which it
requires, leads it to move about very little, so that it uses its
legs only to stand on the ground, to walk, or run, and they never
serve to seize hold of or to climb trees.
"From this habit of daily consuming great amounts of food which
distend the organs which receive it, and of only moving about to a
limited extent, it has resulted that the bodies of these animals are
thick, clumsy, and massive, and have acquired a very great volume,
as we see in elephants, rhinoceroses, oxen, buffaloes, horses, etc.
"The habit of standing upright on their four feet during the greater
part of the day to browse has given origin to a thick hoof which
envelops the extremity of the digits of their feet; and as their
toes are not trained to make any movement, and because they have
served no other use than as supports, as also the rest of the leg,
the most of them are short, are reduced in size, and even have ended
by totally disappearing. Thus in the _pachyderms_, some have five
toes enveloped in horn, and consequently their foot is divided into
five parts; others have only four, and still others only three. But
in the _ruminants_, which seem to be the most ancient of mammals,
which are limited only to standing on the ground, there are only two
digits on each foot, and only a single one is to be found in the
_solipedes_ (the horse, the ass).
"Moreover, among these herbivorous animals, and especially among the
ruminants, it has been found that from the circumstances of the
desert countries they inhabit they are incessantly exposed to be
the prey of carnivorous animals, and find safety only in precipitous
flight. Necessity has forced them to run swiftly; and from the habit
they have thus acquired their body has become slenderer and their
limbs much more delicate: we see examples in the antelopes, the
gazelles, etc.
"Other dangers in our climate to which are continually exposed the
deer, the roebuck, the fallow-deer, of perishing from the chase made
by man, have reduced them to the same necessity, restrained them to
similar habits, and have given rise to the same results.
"The ruminating animals only using their legs as supports, and not
having strong jaws, which are only exercised in cutting and browsing
on grass, can only fight by striking with the head, by directing
against each other the _vertex_ of this part.
"In their moments of anger, which are frequent, especially among the
males, their internal feelings, by their efforts, more strongly urge
the fluids toward this part of their head, and it there secretes the
corneous matter in some, and osseous matter mixed with corneous
matter in others, which gives origin to solid protuberances; hence
the origin of horns and antlers, with which most of these animals
have the head armed.
"As regards habits, it is curious to observe the results in the
special form and height of the giraffe (_camelopardalis_); we know
that this animal, the tallest of mammals, inhabits the interior of
Africa, and that it lives in localities where the earth, almost
always arid and destitute of herbage, obliges it to browse on the
foliage of trees, and to make continual efforts to reach it. It has
resulted from this habit, maintained for a long period in all the
individuals of its race, that its forelegs have become longer than
the hinder ones, and that its neck is so elongated that the
giraffe, without standing on its hind legs, raises its head and
reaches six meters in height (almost twenty feet).
"Among the birds, the ostriches, deprived of the power of flight,
and raised on very long legs, probably owe their singular
conformation to analogous circumstances.
"The result of habits is as remarkable in the carnivorous mammals as
it is in the herbivorous, but it presents effects of another kind.
"Indeed, those of these mammals which are habituated, as their race,
both to climb as well as to scratch or dig in the ground, or to tear
open and kill other animals for food, have been obliged to use the
digits of their feet; moreover, this habit has favored the
separation of their digits, and has formed the claws with which they
are armed.
"But among the carnivores there are some which are obliged to run in
order to overtake their prey; moreover, since these need and
consequently have the habit of daily tearing with their claws and
burying them deeply in the body of another animal, to seize and then
to tear the flesh, and have been enabled by their repeated efforts
to procure for these claws a size and curvature which would greatly
interfere in walking or running on stony soil, it has resulted in
this case that the animal has been obliged to make other efforts to
draw back these too salient and curved claws which would impede it,
and hence there has resulted the gradual formation of those special
sheaths in which the cats, tigers, lions, etc., withdraw their claws
when not in action.
"Thus the efforts in any direction whatever, maintained for a long
time or made habitually by certain parts of a living body to satisfy
necessities called out by nature or by circumstances, develop these
parts and make them acquire dimensions and a shape which they never
would have attained if these efforts had not become the habitual
action of the animals which have exercised them. The observations
made on all the animals known will everywhere furnish examples.
"Can any of them be more striking than that which the _kangaroo_
offers us? This animal, which carries its young in its abdominal
pouch, has adopted the habit of holding itself erect, standing only
on its hind feet and tail, and only changing its position by a
series of leaps, in which it preserves its erect attitude so as not
to injure its young.
"Let us see the result:
"1. Its fore legs, of which it makes little use, and on which it
rests only during the instant when it leaves its erect attitude,
have never reached a development proportionate to that of the other
parts, and have remained thin, very small, and weak;
"2. The hind legs, almost continually in action, both for supporting
the body and for leaping, have, on the contrary, obtained a
considerable development, and have become very large and strong;
"3. Finally, the tail, which we see is of much use in supporting the
animal and in the performance of its principal movements, has
acquired at its base a thickness and a strength extremely
remarkable.
"These well-known facts are assuredly well calculated to prove what
results from the habitual use in the animals of any organ or part;
and if, when there is observed in an animal an organ especially well
developed, strong, and powerful, it is supposed that its habitual
use has not produced it, that its continual disuse will make it lose
nothing, and, finally, that this organ has always been such since
the creation of the species to which this animal belongs, I will ask
why our domestic ducks cannot fly like wild ducks--in a word, I
might cite a multitude of examples which prove the differences in us
resulting from the exercise or lack of use of such of our organs,
although these differences might not be maintained in the
individuals which follow them genetically, for then their products
would be still more considerable.
"I shall prove, in the second part, that when the will urges an
animal to any action, the organs which should execute this action
are immediately provoked by the affluence of subtile fluids (the
nervous fluid), which then become the determining cause which calls
for the action in question. A multitude of observations prove this
fact, which is now indisputable.
"It results that the multiplied repetitions of these acts of
organization strengthen, extend, develop, and even create the organs
which are necessary. It is only necessary attentively to observe
that which is everywhere occurring to convince ourselves of the
well-grounded basis of this cause of organic developments and
changes.
"Moreover, every change acquired in an organ by a habit of use
sufficient to have produced it is then preserved by heredity
(_génération_) if it is common to the individuals which, in
fecundation, unite in the reproduction of their species. Finally,
this change is propagated, and thus is transmitted to all the
individuals which succeed and which are submitted to the same
circumstances, unless they have been obliged to acquire it by the
means which have in reality created it.
"Besides, in reproductive unions the crossings between the
individuals which have different qualities or forms are necessarily
opposed to the continuous propagation of these qualities and these
forms. We see that in man, who is exposed to so many diverse
circumstances which exert an influence on him, the qualities or the
accidental defects which he has been in the way of acquiring, are
thus prevented from being preserved and propagated by generation.
If, when some particular features of form or any defects are
acquired, two individuals under this condition should always pair,
they would reproduce the same features, and the successive
generations being confined to such unions, a special and distinct
race would then be formed. But perpetual unions between individuals
which do not have the same peculiarities of form would cause all the
characteristics acquired by special circumstances to disappear.
"From this we can feel sure that if distances of habitation did not
separate men the intermixture by generation would cause the general
characteristics which distinguish the different nations to
disappear.
"If I should choose to pass in review all the classes, all the
orders, all the genera, and all the species of animals which exist,
I should show that the structure of individuals and their parts,
their organs, their faculties, etc., etc., are in all cases the sole
result of the circumstances in which each species is found to be
subjected by nature and by the habits which the individuals which
compose it have been obliged to contract, and which are only the
product of a power primitively existing, which has forced the
animals into their well-known habits.
"We know that the animal called the _ai_, or the sloth (_Bradypus
tridactylus_), is throughout life in a condition so very feeble that
it is very slow and limited in its movements, and that it walks on
the ground with much difficulty. Its movements are so slow that it
is thought that it cannot walk more than fifty steps in a day. It is
also known that the structure of this animal is in direct relation
with its feeble state or its inaptitude for walking; and that should
it desire to make any other movements than those which it is seen to
make, it could not do it.
"Therefore, supposing that this animal had received from nature its
well-known organization, it is said that this organization has
forced it to adopt the habits and the miserable condition it is in.
"I am far from thinking so; because I am convinced that the habits
which the individuals of the race of the _ai_ were originally
compelled to contract have necessarily brought their organization
into its actual state.
"Since continual exposure to dangers has at some time compelled the
individuals of this species to take refuge in trees and to live in
them permanently, and then feed on their leaves, it is evident that
then they would give up making a multitude of movements that animals
which live on the ground perform.
"All the needs of the _ai_ would then be reduced to seizing hold of
the branches, to creeping along them or to drawing them in so as to
reach the leaves, and then to remain on the tree in a kind of
inaction, so as to prevent falling. Besides, this kind of
sluggishness would be steadily provoked by the heat of the climate;
for in warm-blooded animals the heat urges them rather to repose
than to activity.
"Moreover, during a long period of time the individuals of the race
of the _ai_ having preserved the habit of clinging to trees and of
making only slow and slightly varied movements, just sufficient for
their needs, their organization has gradually become adapted to
their new habits, and from this it will result:
"1. That the arms of these animals making continual efforts readily
to embrace the branches of trees, would become elongated;
"2. That the nails of their digits would acquire much length and a
hooked shape, by the continued efforts of the animal to retain its
hold;
"3. That their digits never having been trained to make special
movements, would lose all mobility among themselves, would become
united, and would only preserve the power of bending or of
straightening out all together;
"4. That their thighs, continually embracing both the trunks and the
larger branches of trees, would contract a condition of habitual
separation which would tend to widen the pelvis and to cause the
cotyloid cavities to be directed backward;
"5. Finally, that a great number of their bones would become fused,
and hence several parts of their skeleton would assume an
arrangement and a figure conformed to the habits of these animals,
and contrary to what would be necessary for them to have for other
habits.
"Indeed, this can never be denied, because, in fact, nature on a
thousand other occasions shows us, in the power exercised by
circumstances on habits, and in that of the influence of habits on
forms, dispositions, and the proportion of the parts of animals,
truly analogous facts.
"A great number of citations being unnecessary, we now see to what
the case under discussion is reduced.
"The fact is that divers animals have each, according to their genus
and their species, special habits, and in all cases an organization
which is perfectly adapted to these habits.
"From the consideration of this fact, it appears that we should be
free to admit either one or the other of the following conclusions,
and that only one of them is susceptible of proof.
"_Conclusion admitted up to this day_: Nature (or its Author), in
creating the animals, has foreseen all the possible kinds of
circumstances in which they should live, and has given to each
species an unchanging organization, as also a form determinate and
invariable in its different parts, which compels each species to
live in the places and in the climate where we find it, and has
there preserved its known habits.
"_My own conclusion_: Nature, in producing in succession every
species of animal, and beginning with the least perfect or the
simplest to end her work with the most perfect, has gradually
complicated their structure; and these animals spreading generally
throughout all the inhabitable regions of the globe, each species
has received, through the influence of circumstances to which it has
been exposed, the habits which we have observed, and the
modifications in its organs which observation has shown us it
possesses.
"The first of these two conclusions is that believed up to the
present day--namely, that held by nearly every one; it implies, in
each animal, an unchanging organization and parts which have never
varied, and which will never vary; it implies also that the
circumstances of the places which each species of animal inhabits
will never vary in these localities; for should they vary, the same
animals could not live there, and the possibility of discovering
similar forms elsewhere, and of transporting them there, would be
forbidden.
"The second conclusion is my own: it implies that, owing to the
influence of circumstances on habits, and as the result of that of
habits on the condition of the parts and even on that of the
organization, each animal may receive in its parts and its
organization, modifications susceptible of becoming very
considerable, and of giving rise to the condition in which we find
all animals.
"To maintain that this second conclusion is unfounded, it is
necessary at first to prove that each point of the surface of the
globe never varies in its nature, its aspect, its situation whether
elevated or depressed, its climate, etc., etc.; and likewise to
prove that any part of animals does not undergo, even at the end of
a long period, any modification by changes of circumstances, and by
the necessity which directs them to another kind of life and action
than that which is habitual to them.
"Moreover, if a single fact shows that an animal for a long time
under domestication differs from the wild form from which it has
descended, and if in such a species in domesticity we find a great
difference in conformation between the individuals submitted to
such habits and those restricted to different habits, then it will
be certain that the first conclusion does not conform to the laws of
nature, and that, on the contrary, the second is perfectly in accord
with them.
"Everything combines then to prove my assertion--namely, that it is
not the form, either of the body or of its parts, which gives rise
to habits, and to the mode of life among animals; but that it is on
the contrary the habits, the manner of living, and all the other
influencing circumstances which have, after a time, constituted the
form of the body and of the parts of animals. With the new forms,
new faculties have been acquired, and gradually nature has come to
form the animals as we actually see them.
"Can there be in natural history a consideration more important, and
to which we should give more attention, than that which I have just
stated?
"We will end this first part with the principles and the exposition
of the natural classification of animals."
In the fourth chapter of the third part (vol. ii. pp. 276-301) Lamarck
treats of the internal feelings of certain animals, which provoke wants
(_besoins_). This is the subject which has elicited so much adverse
criticism and ridicule, and has in many cases led to the wholesale
rejection of all of Lamarck's views. It is generally assumed or stated
by Lamarck's critics, who evidently did not read his book carefully,
that while he claimed that the plants were evolved by the direct action
of the physical factors, that in the case of all the animals the process
was indirect. But this is not correct. He evidently, as we shall see,
places the lowest animals, those without (or what he supposed to be
without) a nervous system, in the same category as the plants. He
distinctly states at the outset that only certain animals and man are
endowed with this singular faculty, "which consists in being able to
experience _internal emotions_ which provoke the wants and different
external or internal causes, and which give birth to the power which
enables them to perform different actions."
"The nervous fluid," he says, "can, then, undergo movements in certain
parts of its mass, as well as in every part at once; moreover, it is
these latter movements which constitute the _general movements_
(_ébranlements_) of this fluid, and which we now proceed to consider.
"The general movements of the nervous fluid are of two kinds;
namely,
"1. Partial movements (_ébranlements_), which finally become general
and end in a reaction. It is the movements of this sort which
produce feeling. We have treated of them in the third chapter.
"2. The movements which are general from the time they begin, and
which form no reaction. It is these which constitute internal
emotions, and it is of them alone of which we shall treat.
"But previously, it is necessary to say a word regarding the
_feeling of existence_, because this feeling is the source from
which the inner emotions originate.
"_On the Feeling of Existence._
"The feeling of existence (_sentiment d'existence_), which I shall
call _inner feeling_,[183] so as to separate from it the idea of a
general condition (_généralité_) which it does not possess, since it
is not common to all living beings and not even to all animals, is
a very obscure feeling, with which are endowed those animals
provided with a nervous system sufficiently developed to give them
the faculty of feeling.
"This sentiment, very obscure as it is, is nevertheless very
powerful, for it is the source of inner emotions which test
(_éprouvent_) the individuals possessing it, and, as the result,
this singular force urges these individuals to themselves produce
the movements and the actions which their wants require. Moreover
this feeling, considered as a very active _motor_, only acts thus by
sending to the muscles which necessarily cause these movements and
actions the nervous fluid which excites them....
"Indeed, as the result of organic or vital movements which are
produced in every animal, that which possesses a nervous system
sufficiently developed has physical sensibility and continually
receives in every inner and sensitive part impressions which
continually affect it, and which it feels in general without being
able to distinguish any single one.
"The sentiment of existence [consciousness] is general, since almost
every sensitive part of the body shares in it. 'It constitutes this
_me_ (_moi_) with which all animals, which are only sensitive, are
penetrated, without perceiving it, but which those possessing a
brain are able to notice, having the power of thought and of giving
attention to it. Finally, it is in all the source of a power which
is aroused by wants, which acts effectively only by emotion, and
through which the movements and actions derive the force which
produces them'....
"Finally, the inner feeling only manifests its power, and causes
movements, when there exists a system for muscular movement, which
is always dependent on the nervous system, and cannot take place
without it."
The author then states that these emotions of the organic sense may
operate in the animals and in man either without or with an act of their
will.
"From what has been said, we cannot doubt but that the inner and
general feeling which urges the animals possessing a nervous system
fitted for feeling should be susceptible of being aroused by the
causes which affect it; moreover, these causes are always the need
both of satisfying hunger, of escaping dangers, of avoiding pain, of
seeking pleasure, or that which is agreeable to the individual, etc.
"The emotions of the inner feeling can only be recognized by man,
who alone pays attention to them, but he only perceives those which
are strong, which excite his whole being, such as a view from a
precipice, a tragic scene, etc."
Lamarck then divides the emotions into physical and moral, the latter
arising from our ideas, thoughts--in short, our intellectual acts--in
the account of which we need not follow him.
In the succeeding chapter (V.) the author dilates on the force which
causes actions in animals. "We know," he says "that plants can satisfy
their needs without moving, since they find their food in the environing
_milieux_. But it is not the same with animals, which are obliged to
move about to procure their sustenance. Moreover, most of them have
other wants to satisfy, which require other kinds of movements and
acts." This matter is discussed in the author's often leisurely and
prolix way, with more or less repetition, which we will condense.
The lowest animals--those destitute of a nervous system--move in
response to a stimulus from without. Nature has gradually created the
different organs of animals, varying the structure and situation of
these organs according to circumstances, and has progressively improved
their powers. She has begun by borrowing from without, so to speak--from
the environment--the _productive force_, both of organic movements and
those of the external parts. "She has thus transported this force [the
result of heat, electricity, and perhaps others (p. 307)] into the
animal itself, and, finally, in the most perfect animals she has placed
a great part of this force at their disposal, as I will soon show."
This force incessantly introduced into the lowest animals sets in motion
the visible fluids of the body and excites the irritability of their
contained parts, giving rise to different contractile movements which we
observe; hence the appearance of an irresistible propensity (_penchant_)
which constrains them to execute those movements which by their
continuity or their repetition give rise to habits.
The most imperfect animals, such as the _Infusoria_, especially the
monads, are nourished by absorption and by "an internal inhibition of
absorbed matters." "They have," he says, "no power of seeking their
food, they have not even the power of recognizing it, but they absorb it
because it comes in contact with every side of them (_avec tous les
points de leur individu_), and because the water in which they live
furnishes it to them in sufficient abundance."
"These frail animals, in which the subtile fluids of the environing
_milieux_ constitute the stimulating cause of the orgasm, of
irritability and of organic movements, execute, as I have said,
contractile movements which, provoked and varied without ceasing by this
stimulating cause, facilitate and hasten the absorptions of which I have
just spoken." ...
_On the Transportation of the force-producing Movements in the Interior
of Animals._
"If nature were confined to the employment of its first
means--namely, of a force entirely external and foreign to the
animal--its work would have remained very important; the animals
would have remained machines totally passive, and she would never
have given origin in any of these living beings to the admirable
phenomena of sensibility, of inmost feelings of existence which
result therefrom, of the power of action, finally, of ideas, by
which she can create the most wonderful of all, that of thought--in
a word, intelligence.
"But, wishing to attain these grand results, she has by slow degrees
prepared the means, in gradually giving consistence to the internal
parts of animals; in differentiating the organs, and in multiplying
and farther forming the fluids contained, etc., after which she has
transported into the interior of these animals that force productive
of movements and of actions which in truth it would not dominate at
first, but which she has come to place, in great part, at their
disposition when their organization should become very much more
perfect.
"Indeed, from the time that the animal organization had sufficiently
advanced in its structure to possess a nervous system--even slightly
developed, as in insects--the animals provided with this
organization were endowed with an intimate sense of their existence,
and from that time the force productive of movements was conveyed
into the very interior of the animal.
"I have already made it evident that this internal force which
produces movements and actions should derive its origin in the
intimate feeling of existence which animals with a nervous system
possess, and that this feeling, solicited or aroused by needs,
should then start into motion the subtile fluid contained in the
nerves and carry it to the muscles which should act, this producing
the actions which the needs require.
"Moreover, every want felt produces an emotion in the inner feeling
of the individual which experiences it; and from this emotion of the
feeling in question arises the force which gives origin to the
movement of the parts which are placed in activity....
"Thus, in the animals which possess the power of acting--namely, the
force productive of movements and actions--the inner feeling, which
on each occasion originates this force, being excited by some need,
places in action the power or force in question; excites the
movement of displacement in the subtile fluid of the nerves--which
the ancients called _animal spirits_; directs this fluid towards
that of its organs which any want impels to action; finally makes
this same fluid flow back into its habitual reservoirs when the
needs no longer require the organ to act.
"The inner feeling takes the place of the _will_; for it is now
important to consider that every animal which does not possess the
special organ in which or by which it executes thoughts, judgments,
etc., has in reality no will, does not make a choice, and
consequently cannot control the movements which its inner feeling
excites. _Instinct_ directs these actions, and we shall see that
this direction always results from emotions of the inner feeling, in
which intelligence has no part, and from the organization even which
the habits have modified, in such a manner that the needs of animals
which are in this category, being necessarily limited and always
the same in the same species, the inner feeling and, consequently,
the power of acting, always produces the same actions.
"It is not the same in animals which besides a nervous system have a
brain [the author meaning the higher vertebrates], and which make
comparisons, judgments, thoughts, etc. These same animals control
more or less their power of action according to the degree of
perfection of their brain; and although they are still strongly
subjected to the results of their habits, which have modified their
structure, they enjoy more or less freedom of the will, can choose,
and can vary their acts, or at least some of them."
Lamarck then treats of the consumption and exhaustion of the nervous
fluid in the production of animal movements, resulting in fatigue.
He next occupies himself with the origin of the inclination to the same
actions, and of instinct in animals.
"The cause of the well-known phenomenon which constrains almost all
animals to always perform the same acts, and that which gives rise
in man to a propensity (_penchant_) to repeat every action, becoming
habitual, assuredly merits investigation.
"The animals which are only 'sensible'[184]--namely, which possess
no brain, cannot think, reason, or perform intelligent acts, and
their perceptions being often very confused--do not reason and can
scarcely vary their actions. They are, then, invariably bound by
habits. Thus the insects, which of all animals endowed with feeling
have the least perfect nervous system,[185] have perceptions of
objects which affect them, and seem to have memory of them when they
are repeated. Yet they can vary their actions and change their
habits, though they do not possess the organ whose acts could give
them the means.
"_On the Instincts of Animals._
"We define instinct as the sum (_ensemble_) of the decisions
(_déterminations_) of animals in their actions; and, indeed, some
have thought that these determinations were the product of a
rational choice, and consequently the fruit of experience. Others,
says Cabanis, may think with the observers of all ages that several
of these decisions should not be ascribed to any kind of reasoning,
and that, without ceasing as for that to have their source in
physical sensibility, they are most often formed without the will of
the individuals able to have any other part than in better directing
the execution. It should be added, without the will having any part
in it; for when it does not act, it does not, of course, direct the
execution.
"If it had been considered that all the animals which enjoy the
power of sensation have their inner feeling susceptible of being
aroused by their needs, and that the movements of their nervous
fluids, which result from these emotions, are constantly directed by
this inner sentiment and by habits, then it has been felt that in
all the animals deprived of intelligence all the decisions of action
can never be the result of a rational choice, of judgment, of
profitable experience--in a word, of will--but that they are
subjected to needs which certain sensations excite, and which awaken
the inclinations which urge them on.
"In the animals even which enjoy the power of performing certain
intelligent acts, it is still more often the inner feeling and the
inclinations originating from habits which decide, without choice,
the acts which animals perform.
"Moreover, although the executing power of movements and of actions,
as also the cause which directs them, should be entirely internal,
it is not well, as has been done,[186] to limit to internal
impressions the primary cause or provocation of these acts, with the
intention to restrict to external impressions that which provokes
intelligent acts; for, from what few facts are known bearing on
these considerations, we are convinced that, either way, the causes
which arouse and provoke acts are sometimes internal and sometimes
external, that these same causes give rise in reality to impressions
all of which act internally.
"According to the idea generally attached to the word _instinct_ the
faculty which this word expresses is considered as a light which
illuminates and guides animals in their actions, and which is with
them what reason is to us. No one has shown that instinct can be a
force which calls into action; that this force acts effectively
without any participation of the will, and that it is constantly
directed by acquired inclinations."
There are, the author states, two kinds of causes which can arouse the
inner feeling (organic sense)--namely, those which depend on
intellectual acts, and those which, without arising from it, immediately
excite it and force it to direct its power of acting in the direction of
acquired inclinations.
"These are the only causes of this last kind, which constitute all
the acts of _instinct_; and as these acts are not the result of
deliberation, of choice, of judgment, the actions which arise from
them always satisfy, surely and without error, the wants felt and
the propensities arising from habits.
"Hence, _instinct_ in animals is an inclination which necessitates
that from sensations provoked while giving rise to wants the animal
is impelled to act without the participation of any thought or any
act of the will.
"This propensity owes to the organization what the habits have
modified in its favor, and it is excited by impressions and wants
which arouse the organic sense of the individual and put it in the
way of sending the nervous fluid in the direction which the
propensity in activity needs to the muscles to be placed in action.
"I have already said that the habit of exercising such an organ, or
such a part of the body, to satisfy the needs which often spring up,
should give to the subtile fluid which changes its place where is to
be operated the power which causes action so great a facility in
moving towards this organ, where it has been so often employed, that
this habit should in a way become inherent in the nature of the
individual, which is unable to change it.
"Moreover, the wants of animals possessing a nervous system being,
in each case, dependent on the Structure of these organisms, are:
"1. Of obtaining any kind of food;
"2. Of yielding to sexual fecundation which excites in them certain
sensations;
"3. Of avoiding pain;
"4. Of seeking pleasure or happiness.
"To satisfy these wants they contract different kinds of habits,
which are transformed into so many propensities, which they can
neither resist nor change. From this originate their habitual
actions, and their special propensities to which we give the name
of instinct.[187]
"This propensity of animals to preserve their habits and to renew
the actions resulting from them being once acquired, is then
propagated by means of reproduction or generation, which preserves
the organization and the disposition of parts in the state thus
attained, so that this same propensity already exists in the new
individuals even before they have exercised it.
"It is thus that the same habits and the same _instinct_ are
perpetuated from generation to generation in the different species
or races of animals, without offering any notable variation,[188] so
long as it does not suffer change in the circumstances essential to
the mode of life."
"_On the Industry of Certain Animals._
"In those animals which have no brain that which we call _industry_
as applied to certain of their actions does not deserve such a name,
for it is a mistake to attribute to them a faculty which they do not
possess.
"Propensities transmitted and received by heredity (_génération_);
habits of performing complicated actions, and which result from
these acquired propensities; finally, different difficulties
gradually and habitually overcome by as many emotions of the organic
sense (_sentiment intérieur_), constitute the sum of actions which
are always the same in the individuals of the same race, to which we
inconsiderately give the name of _industry_.
"The instinct of animals being formed by the habit of satisfying the
four kinds of wants mentioned above, and resulting from the
propensities acquired for a long time which urge them on in a way
determined for each species, there comes to pass, in the case of
some, only a complication in the actions which can satisfy these
four kinds of wants, or certain of them, and, indeed, only the
different difficulties necessary to be overcome have gradually
compelled the animal to extend and make contrivances, and have led
it, without choice or any intellectual act, but only by the emotions
of the organic sense, to perform such and such acts.
"Hence the origin, in certain animals, of different complicated
actions, which has been called _industry_, and which are so
enthusiastically admired, because it has always been supposed, at
least tacitly, that these actions were contrived and deliberately
planned, which is plainly erroneous. They are evidently the fruit of
a necessity which has expanded and directed the habits of the
animals performing them, and which renders them such as we observe.
"What I have just said is especially applicable to the invertebrate
animals, in which there enters no act of intelligence. None of
these can indeed freely vary its actions; none of them has the power
of abandoning what we call its _industry_ to adopt any other kind.
"There is, then, nothing wonderful in the supposed industry of the
ant-lion (_Myrmeleon formica-leo_), which, having thrown up a
hillock of movable sand, waits until its booty is thrown down to the
bottom of its funnel by the showers of sand to become its victim;
also there is none in the manoeuvre of the oyster, which, to
satisfy all its wants, does nothing but open and close its shell. So
long as their organization is not changed they will always, both of
them, do what we see them do, and they will do it neither
voluntarily nor rationally.
"This is not the case with the vertebrate animals, and it is among
them, especially in the birds and mammals, that we observe in their
actions traces of a true _industry_; because in difficult cases
their intelligence, in spite of their propensity to habits, can aid
them in varying their actions. These acts, however, are not common,
and are only slightly manifested in certain races which have
exercised them more, as we have had frequent occasion to remark."
Lamarck then (chapter vi.) examines into the nature of the _will_, which
he says is really the principle underlying all the actions of animals.
The will, he says, is one of the results of thought, the result of a
reflux of a portion of the nervous fluid towards the parts which are to
act.
He compares the brain to a register on which are imprinted ideas of all
kinds acquired by the individual, so that this individual provokes at
will an effusion of the nervous fluid on this register, and directs it
to any particular page. The remainder of the second volume
(chapter vii.) is devoted to the understanding, its origin and that of
ideas. The following additions relative to chapters vii. and viii. of
the first part of this work are from vol. ii., pp. 451-466.
In the last of June, 1809, the menagerie of the Museum of Natural
History having received a Phoca (_Phoca vitulina_), Lamarck, as he says,
had the opportunity of observing its movements and habits. After
describing its habits in swimming and moving on land and observing its
relation to the clawed mammals, he says his main object is to remark
that the seals do not have the hind legs arranged in the same direction
as the axis of their body, because these animals are constrained to
habitually use them to form a caudal fin, closing and widening, by
spreading their digits, the paddle (_palette_) which results from their
union.
"The morses, on the contrary, which are accustomed to feed on grass
near the shore, never use their hind feet as a caudal fin; but their
feet are united together with the tail, and cannot separate. Thus in
animals of similar origin we see a new proof of the effect of habits
on the form and structure of organs."
He then turns to the flying mammals, such as the flying squirrel
(_Sciurus volans_, _ærobates_, _petaurista_, _sagitta_, and
_volucella_), and then explains the origin of their adaptation for
flying leaps.
"These animals, more modern than the seals, having the habit of
extending their limbs while leaping to form a sort of _parachute_,
can _only_ make a very prolonged leap when they glide down from a
tree or spring only a short distance from one tree to another. Now,
by frequent repetitions of such leaps, in the individuals of these
races the skin of their sides is expanded on each side into a loose
membrane, which connects the hind and fore legs, and which,
enclosing a volume of air, prevents their sudden falling. These
animals are, moreover, without membranes between the fingers and
toes.
"The Galeopithecus (_Lemur volans_), undoubtedly a more ancient form
but with the same habits as the flying squirrel (_Pteromys Geoff._),
has the skin of the _flancs_ more ample, still more developed,
connecting not only the hinder with the fore legs, but in addition
the fingers and the tail with the hind feet. Moreover, they leap
much farther than the flying squirrels, and even make a sort of
flight.[189]
"Finally, the different bats are probably mammals still older than
the Galeopithecus, in the habit of extending their membrane and even
their fingers to encompass a greater volume of air, so as to sustain
their bodies when they fly out into the air.
"By these habits, for so long a period contracted and preserved, the
bats have obtained not only lateral membranes, but also an
extraordinary elongation of the fingers of their fore feet (with the
exception of the thumb), between which are these very ample
membranes uniting them; so that these membranes of the hands become
continuous with those of the flanks, and with those which connect
the tail with the two hind feet, forming in these animals great
membranous wings with which they fly perfectly, as everybody knows.
"Such is then the power of habits, which have a singular influence
on the conformation of parts, and which give to the animals which
have for a long time contracted certain of them, faculties not found
in other animals.
"As regards the amphibious animals of which I have often spoken, it
gives me pleasure to communicate to my readers the following
reflections which have arisen from an examination of all the objects
which I have taken into consideration in my studies, and seen more
and more to be confirmed.
"I do not doubt but that the mammals have in reality originated from
them, and that they are the veritable cradle (_berceau_) of the
entire animal kingdom.
"Indeed, we see that the least perfect animals (and they are the
most numerous) live only in the water; hence it is probable, as I
have said (vol. ii., p. 85), that it is only in the water or in very
humid places that nature causes and still forms, under favorable
conditions, direct or spontaneous generations which have produced
the simplest animalcules and those from which have successively been
derived all the other animals.
"We know that the Infusoria, the polyps, and the Radiata only live
in the water; that the worms even only live some in the water and
others in very damp places.
"Moreover, regarding the worms, which seem to form an initial branch
of the animal scale, since it is evident that the Infusoria form
another branch, we may suppose that among those of them which are
wholly aquatic--namely, which do not live in the bodies of other
animals, such as the Gordius and many others still unknown--there
are doubtless a great many different aquatic forms; and that among
these aquatic worms, those which afterwards habitually expose
themselves to the air have probably produced amphibious insects,
such as the mosquitoes, the ephemeras, etc., etc., which have
successively given origin to all the insects which live solely in
the air. But several races of these having changed their habits by
the force of circumstances, and having formed habits of a life
solitary, retired, or hidden, have given rise to the arachnides,
almost all of which also live in the air.
"Finally, those of the arachnides which have frequented the water,
which have consequently become progressively habituated to live in
it, and which finally cease to expose themselves to the air--this
indicates the relations which, connecting the Scolopendræ to Julus,
this to the Oniscus, and the last to Asellus, shrimps, etc., have
caused the existence of all the Crustacea.
"The other aquatic worms which are never exposed to the air,
multiplying and diversifying their races with time, and gradually
making progress in the complication of their structure, have caused
the formation of the Annelida, Cirripedia, and molluscs, which
together form an uninterrupted portion of the animal scale.
"In spite of the considerable hiatus which we observe between the
known molluscs and the fishes, the molluscs, whose origin I have
just indicated, have, by the intermediation of those yet remaining
unknown, given origin to the fishes, as it is evident that the
latter have given rise to the reptiles.
"In continuing to consult the probabilities on the origin of
different animals, we cannot doubt but that the reptiles, by two
distinct branches which circumstances have brought about, have given
rise on one side to the formation of birds, and on the other to
that of amphibious mammals, which have given in their turn origin to
all the other mammals.[190]
"Indeed, the fishes having caused the formation of Batrachia, and
these of the Ophidian reptiles, both having only one auricle in the
heart, nature has easily come to give a heart with a double auricle
to other reptiles which constitute two special branches; finally,
she has easily arrived at the end of forming, in the animals which
had originated from each of these branches, a heart with two
ventricles.
"Thus, among the reptiles whose heart has a double auricle, on the
one side, the Chelonians seem to have given origin to the birds; if,
independently of several relations which we cannot disregard, I
should place the head of a tortoise on the neck of certain birds, I
should perceive almost no disparity in the general physiognomy of
the factitious animal; and on the other side, the saurians,
especially the 'planicaudes,' such as the crocodiles, seem to have
given origin to the amphibious mammals.
"If the branch of the Chelonians has given rise to birds, we can yet
presume that the palmipede aquatic birds, especially the
_brevipennes_, such as the penguins and the _manchots_, have given
origin to the monotremes.
"Finally, if the branch of saurians has given rise to the amphibious
mammals, it will be most probable that this branch is the source
whence all the mammals have taken their origin.
"I therefore believe myself authorized to think that the terrestrial
mammals originally descended from those aquatic mammals that we call
Amphibia. Because the latter being divided into three branches by
the diversity of the habits which, with the lapse of time, they have
adopted, some have caused the formation of the Cetacea, others that
of the ungulated mammals, and still others that of the unguiculate
mammals.
"For example, those of the Amphibia which have preserved the habit
of frequenting the shores differ in the manner of taking their food.
Some among them accustoming themselves to browse on herbage, such as
the morses and lamatines, gradually gave origin to the ungulate
mammals, such as the pachyderms, ruminants, etc.; the others, such
as the Phocidæ, contracting the habit of feeding on fishes and
marine animals, caused the existence of the unguiculate mammals, by
means of races which, while becoming differentiated, became entirely
terrestrial.
"But those aquatic mammals which would form the habit of never
leaving the water, and only rising to breathe at the surface, would
probably give origin to the different known cetaceans. Moreover, the
ancient and complete habitation of the Cetacea in the ocean has so
modified their structure that it is now very difficult to recognize
the source whence they have derived their origin.
"Indeed, since the enormous length of time during which these
animals have lived in the depths of the sea, never using their hind
feet in seizing objects, their disused feet have wholly disappeared,
as also their skeleton, and even the pelvis serving as their
attachment.
"The alteration which the cetaceans have undergone in their limbs,
owing to the influence of the medium in which they live and the
habits which they have there contracted, manifests itself also in
their fore limbs, which, entirely enveloped by the skin, no longer
show externally the fingers in which they end; so that they only
offer on each side a fin which contains concealed within it the
skeleton of a hand.
"Assuredly, the cetaceans being mammals, it entered into the plan of
their structure to have four limbs like the others, and
consequently a pelvis to sustain their hind legs. But here, as
elsewhere, that which is lacking in them is the result of atrophy
brought about, at the end of a long time, by the want of use of the
parts which were useless.
"If we consider that in the Phocæ, where the pelvis still exists,
this pelvis is impoverished, narrowed, and with no projections on
the hips, we see that the lessened (_médiocre_) use of the hind feet
of these animals must be the cause, and that if this use should
entirely cease, the hind limbs and even the pelvis would in the end
disappear.
"The considerations which I have just presented may doubtless appear
as simple conjectures, because it is possible to establish them only
on direct and positive proofs. But if we pay any attention to the
observations which I have stated in this work, and if then we
examine carefully the animals which I have mentioned, as also the
result of their habits and their surroundings, we shall find that
these conjectures will acquire, after this examination, an eminent
probability.
"The following _tableau_[191] will facilitate the comprehension of
what I have just stated. It will be seen that, in my opinion, the
animal scale begins at least by two special branches, and that in
the course of its extent some branchlets (_rameaux_) would seem to
terminate in certain places.
"This series of animals beginning with two branches where are
situated the most imperfect, the first of these branches received
their existence only by direct or spontaneous generation.
"A strong reason prevents our knowing the changes successively
brought about which have produced the condition in which we observe
them; it is because we are never witnesses of these changes. Thus we
see the work when done, but never watching them during the process,
we are naturally led to believe that things have always been as we
see them, and not as they have progressively been brought about.
"Among the changes which nature everywhere incessantly produces in
her _ensemble_, and her laws remain always the same, such of these
changes as, to bring about, do not need much more time than the
duration of human life, are easily understood by the man who
observes them; but he cannot perceive those which are accomplished
at the end of a considerable time.
"If the duration of human life only extended to the length of a
_second_, and if there existed one of our actual clocks mounted and
in movement, each individual of our species who should look at the
hour-hand of this clock would never see it change its place in the
course of his life, although this hand would really not be
stationary. The observations of thirty generations would never learn
anything very evident as to the displacement of this hand, because
its movement, only being that made during half a minute, would be
too slight to make an impression; and if observations much more
ancient should show that this same hand had really moved, those who
should see the statement would not believe it, and would suppose
there was some error, each one having always seen the hand on the
same point of the dial-plate.
"I leave to my readers all the applications to be made regarding
this supposition.
"_Nature_, that immense totality of different beings and bodies, in
every part of which exists an eternal circle of movements and
changes regulated by law; totality alone unchangeable, so long as it
pleases its SUBLIME AUTHOR to make it exist, should be regarded as a
whole constituted by its parts, for a purpose which its Author alone
knows, and not exclusively for any one of them.