Zoological Philosophy
by
J. B. Lamarck
[This translation, which has been prepared by Ian
Johnston of Malaspina University-College, Nanaimo,
BC, Canada, (now Vancouver Island University) is in the public domain, and may
be used by anyone, in whole or in part, without permission and without charge,
provided the source is acknowledged, released September 1999]
First Part
Considerations of the Natural
History of Animals, Their Characteristics, Their Interrelationships, Their
Organic Structure, Their Distribution, Their Classification and Their Species
Chapter Five
On the Present State of the
Distribution and Classification of Animals
For
the progress of Philosophical Zoology and for the goal which we have in mind,
it is necessary to consider the present state of the distribution and
classification of animals, to examine how we have arrived at it, to recognize
what the principles are to which we had to conform to establish this universal
distribution, and finally to study what remains to accomplish to give this
distribution the most appropriate character so as to make it depict the order
of nature itself.
But to
derive some benefit from all these matters, we must first determine the
essential purpose of the distribution of animals and of their classification,
because these two purposes have very different natures.
The
purpose of a general distribution of animals is not only to obtain a convenient
list to consult, but above all to have in this list an order which represents,
as much as possible, the very order of nature, that is to say, the order which
nature has very clearly characterized by the relationships which she has
established between the animals.
The
aim of a classification of animals, by contrast, is to furnish, with the help
of lines of separation traced in various places in the general series of
creatures, points where our imagination can stop so that we can more easily
recognize each race which has already been observed, grasp the interconnections
with the other known animals, and place in each group the new species which we
succeed in discovering. This method compensates our weaknesses, makes our
studies and our understanding easier, and its use is indispensably necessary to
us. But I have already shown that it is a product of art and that, despite any
appearance to the contrary, it has no real connection with nature.
The
proper determination of the interconnections between things will always
invariably establish in our general distributions, first, the place of the
large groups or the primary divisions and, second, that of the groups subordinate
to the first and, finally, that of the species or the particular races which
have been observed. Now, there you see the inestimable advantage for science of
the knowledge of the interrelationships: since these interrelationships are the
work of nature itself, no naturalist would ever have the power or, no doubt,
the desire to change the results of a known interrelationship. The general
distribution thus will become more and more perfect and compelling to the
extent that our understanding of the interconnections advances with respect to
the things which make up a kingdom.
The
case is different with classification, that is to say,
with the different lines of separation which we are concerned to trace from
place to place in the general distribution, whether of animals or plants. In
truth, as long as there will be spaces to fill in our distributions, because
many animals and plants have not yet been observed, we will always find with
these lines of separation that they seem to us created by nature itself. But
this illusion will vanish to the extent that we continue to observe. And
already have we not seen a sufficiently large number of them disappear, at
least in the smallest groups, through the numerous discoveries of naturalists
in roughly the last fifty years?
Thus,
apart from the lines of separation which are the result of gaps which we have
to fill, those which we will always be forced to create will be arbitrary and
hence changeable, as long as naturalists do not adopt some conventional
principle to regulate themselves when they draw such lines.
In the
animal kingdom, we should consider as a conventional regulatory principle the
fact that every class should be understood to consist of animals
characterized by a particular structural system. The strict application of
this principle is easy enough and presents only moderate inconveniences.
In
fact, although nature does not move abruptly from one structural system to
another, it is possible to establish some limits between each system, so that
throughout nature there is only a small number of animals
placed near these limits and in a position to raise some doubts about their
true class.
The
other lines of separation which sub-divide the classes are, in general, more
difficult to fix, because they rest on less important characteristics and, for
this reason, are more arbitrary.
Before
examining the present state of the classification of animals, let me attempt to
show that the distribution of living beings must form a series, at least
with the large groups, and not a ramified network.
The classes must form a series in the distribution of
animals
As
human beings are condemned to go through all possible mistakes before
recognizing one truth when they examine the facts which are relevant to it, people
have denied that the productions of nature in each kingdom of living creatures
were really in the position of being able to form a true series which follows a
consideration of their interrelationships, and we have not wished to recognize
any scale in the general arrangement, whether of animals or plants.
Thus,
since naturalists have noticed that many species, certain genres, and even some
families appear in a sort of isolation so far as their characteristics are
concerned, several of them have imagined that the living creatures in one
kingdom or the other, which according to their natural interconnections are
closely related to or very distant from each other, are distributed like the
different points of a geographical map or a globe. They consider the small and
very pronounced series which have been called natural families as
organized in the form of a network. This idea, which has appeared sublime to
some moderns, is clearly a mistake. And it will undoubtedly disappear as soon
as we have a more profound and more universal understanding of organic
structure, above all when we distinguish what belongs to the influence of
habitats and acquired habits from what is the result of more or less advanced
progress in the composition or the perfecting of organic structures.
In the
meantime, I am going to show that nature gives rise, with the help of a great
deal of time, to the existence of all animals and plants and has really
established in each of these kingdoms a true ladder with respect to the growing
complexity in the organic structure of these living beings, but that this
ladder, which it is our concern to recognize in dealing with these things
according to their natural interrelationships, only offers comprehensible
gradations in the main large groups of the universal series and not in species,
nor even in the genres. The reason for this point stems from the fact that the
extreme diversity of circumstances in which the different races of animals and
plants find themselves is not related to the increasing complexity in the
organic structure among them, as I will show, and that gives rise in their
shapes and exterior characteristics to anomalies or types of leaps which the
increasing complexity in the organic structure could not have brought about by
itself.
It is
therefore a matter of proving that the series which makes up the animal ladder
consists essentially in the distribution of the principle groups which make it
up and not in the distribution of species, nor even in that of the genera.
The series
which I am going to talk about could not therefore be established except in the
placing of the large groups, because these groups which make up the classes and
the large families each consist of beings in which the organic structure
depends upon some particular system of essential organs.
Thus
each distinct large group has its own particular system of essential organs.
And it is these particular systems which are going to deteriorate from the one
which shows the greatest complexity right to the one which is the simplest. But
each organ considered in isolation does not follow such a regular path in its
deterioration. To the extent that the organ has less importance and is more
susceptible to being modified by circumstances, it follows such a path even
less.
In
fact, the organs with little importance or inessential to life are not always
similar to each other in their perfection or degradation, so that if we follow
all the species of a single class, we will see that a particular organ in a
particular species enjoys the highest degree of perfection, while some other
organ which, in this same species, is much impoverished or very imperfect, is
found very perfected in some other species.
These
irregular variations in the perfection and the degradation of non-essential
organs come up in those organs more subject than others to the influence of
external circumstances. This influence brings with it similar variations in the
shape and in the nature of the most external parts and gives rise to such a
large and strangely organized diversity among species, that instead of being
able to arrange them, like the large groups, in a unique series, simple and
linear, in the form of a regularly graduated scale, these same species often
form around the large groups of which they are a part, lateral branches, whose
extremities display truly isolated points.
To
modify each interior system of organic structure requires a more influential
combination of circumstances and a much longer period of time than to modify
and change the external organs.
Nevertheless,
I notice that when circumstance demand, nature goes from one system to another,
without making a jump, provided that the systems are closely related. In fact,
it is by this faculty that nature has managed to form all systems successively,
going from the most simple to the most complex.
It is
so true that nature has this faculty, that it moves from one
system to another, not only in two different families when they are
related by their interconnections, but even in a single individual.
The system of organic structure which include as organs of
respiration real lungs are more closely related to systems which include gills
than those which require tracheae. Thus, not only does nature move from gills
to lungs in the neighboring classes and families, as a consideration of fish
and reptiles shows, but it moves there even during the life of individuals
themselves, who enjoy successively both systems. We know that frogs, in the
imperfect tadpole state, breathe by gills; whereas, in their more perfect
condition as frogs they breathe by lungs. We do not see anywhere nature passing
from a system of tracheae to a pulmonary system.
Thus,
it is true to say that there exists for each kingdom of living beings a unique
and graduated series in the arrangement of the large groups, in conformity with
the increasingly complexity in the organic structure and with the arrangement
of things according to a consideration of the interrelationships and that this
series, whether in the animal or plant kingdom, must offer at its front
extremity the simplest and the least organized living creatures and finish with
the most perfect in structure and faculties.
Such
appears to be the true order of nature, and such is effectively what the most
attentive observation and a sustained study of all the features which
characterize its progress clearly present to us.
Since
the time when, in our distributions of the production of nature, we have felt
it necessary to concern ourselves with the interrelationships, we are no longer
masters at arranging the universal series as we please. The knowledge which we
increasingly acquire of nature’s progress, to the extent that we study the
close or distant interrelationships which it has established, whether between
objects or between their different groups, carries us along with it and forces
us to conform to nature’s order.
The
first result obtained from the use of interrelationships in the placement of
the large groups to form a general distributions is that the two extreme ends
in the order must display the most dissimilar beings, because they are
effectively the most distant so far as such interrelationships are concerned
and, as a result, so far as organic structure is concerned. It follows from
this that if one of the extremities of the order shows living beings developed
in the most perfect way, those in which the organic structure is the most
complex, the other extremity of the same order must necessarily show the most
imperfect living creatures, that is to say, those in which the organic
structure is the simplest.
In the
general disposition of the known plants, according to the natural method, that
is to say, according to the consideration of the interrelationships, as yet we
understand reliably only one of the extremities of the order: we know that the
cryptogram must be located at this extremity. If the other extremity is not
established with the same certainty, that stems from the fact that our
knowledge of the organic structure of plants is much less advanced than what we
understand about a large number of known animals. Consequently, so far as
plants are concerned, we do not yet have a certain guide to determine the
interrelationships between the large groups, of the sort that we have for
recognizing those which exist between the genera and which form the families.
We do
not encounter the same difficulty with the animals. The two extremities of
their general series are determined in a definite way. For as long as we attach
importance to the natural method and, as a result, to the consideration of the
interrelationships, the mammals will necessarily occupy one of the extremities
of the order, whereas, the infusorians will be placed at the other extremity.
Therefore,
there is for animals, as well as for plants, an order which belongs to nature
and which, like the things which this order brings into existence, results from
the methods which nature has received from the Supreme Author of all things. It
is nothing other than the universal immutable order which this Sublime Author
has created in everything, together with the collection of general and
particular laws to which this order is subject. By these means, which nature
continues to use, it has given and perpetually is giving life to its
productions. It varies them and renews them without ceasing, and in this way
maintains the entire order which comes from these means.
We are
going to see that this natural order which we were concerned successfully to
recognize in each kingdom of living beings and of which we already possess
various sections in the well known families and in our best genera, is, so far
as the animal kingdom is concerned, now determined in its entirely in a manner
which leaves no room for anything arbitrary.
But
the large number of the various animals which we have succeeded in
understanding and the numerous insights which comparative anatomy has provided
about their organic structure now give us the means of determining, in a
definitive manner, the general distribution of all the known animals and of assigning
a confirmed rank for the main divisions which we can establish in the series
which they form.
That
is what it is important to recognize and what will be truly difficult to
dispute.
Let us
now move on to an examination of the present state of the general distribution
of animals and of their classification.
The Present State of the Distribution and the Classification
of Animals
Since
the purpose and the principles, whether of the general distribution of living
beings or of their classification, have not been noticed when we concerned
ourselves with these matters, the works of naturalists suffered for a long time
from this imperfection of our ideas. The natural sciences were like all the
others which we busied ourselves with for a long time before thinking about the
principles which must form the basis of the science and govern the work which
goes on in it.
Instead
of subjecting the classification necessary in each kingdom of living creatures
to a distribution which nothing should interfere with, we thought only of
classifying objects conveniently and in this way of subjecting their
distribution to arbitrariness.
For
example, since the connections between the large groups were very difficult to
grasp among the plants, for a long time in botany we used artificial systems.
They made convenient classifications easy to create, based on arbitrary
principles. And each author made up new ones according to his fancy. Thus the
distribution we need to establish among the plants, the one which, in a word,
belongs to the natural method, was then always sacrificed. Only since we have
understood the importance of the parts concerned with the fruit, and above all
the preeminence which certain of those parts must
have over the others, has the general distribution of plants started to
progress towards perfection.
Since
the case is not the same so far as animals are concerned, the general
connections which characterize the large groups are, among themselves, a great
deal easier to perceive. Also several of these groups have been recognized
since the time when we first began to cultivate natural history.
In
fact, Aristotle, at the start, divided the animals in two main groups or,
according to him, two classes, as follows:
1. Animals with Blood
Viviparous
quadrupeds
Oviparous quadrupeds
Fish
Birds
2. Animals without Blood
Mollusks
Crustaceans
Testaceans
Insects
This
primary division of animals into two large groups was good enough, but the
characteristic used by Aristotle in drawing it up was poor. This philosopher gave
the name blood to the principal fluid in animals which is red in colour.
Assuming that since all the animals which belong to his second class possessed
only white or off white fluids, he therefore considered that they lacked blood.
Such
was apparently the first sketch of a classification of animals. It is, at
least, the oldest we know about. But this classification also gives the first
example of a distribution in an sense reversed from
the natural order, since we find in it a progression, although a very imperfect
one, from the most complex to the simplest.
Since
this time, people have generally followed this false direction with regard to
the distribution of animals. And this has clearly held back our knowledge
concerning the nature’s march.
Modern
naturalists believed that they were perfecting Aristotle’s distinction when
they gave to the animals of his first division the name red-blooded animals and
to those of the second division the name white-blooded animals. We are
sufficiently aware now how much this characteristic is defective, since there
are invertebrate animals with red blood (many annelids).
In my
view, the fluids essential to animals cease to merit the name blood as soon as
they no longer circulate in arterial and venous vessels. These fluids are then
so degraded, so lacking in complexity or so imperfect in the combination of
their principles, that we were wrong to link their nature to that of fluids
which undergo a true circulation. Besides, attributing blood to a radiate or to
a polyp means as much as attributing blood to a plant.
To
remove all ambiguity or the use of any hypothetical consideration, in my first
course of study which I carried out in the Museum, in the spring of 1794 (Year
Two of the Republic), I divided all the known animals into two perfectly
distinct groups:
Animals
with backbones
Animals without backbones.
I drew
my students’ attention to the fact that the vertebral column indicates, in the
animals which have it, the possession of a skeleton more or less perfect and of
a structural plan relative to it; whereas, the lack of a vertebral column in
the other animals not only clearly distinguishes them from the first ones, but
announces that the structural plans on which they have been developed were all
very different from those of the vertebrate animals.
From
Aristotle up to Linnaeus, nothing very noteworthy has appeared concerning the
general distribution of animals. But in the last century, some naturalists of
exceeding merit made a large number of particular observations concerning
animals, mainly on a number of animals without vertebrae. Some revealed their
anatomy with more or less detail; others provided an exact and detailed history
of the changes in and the habits of a large number of these animals. As a
result of their valuable observations, we have come to understand many facts of
the highest importance.
Finally
Linnaeus, a man of a superior genius and one of the greatest known naturalists,
after having collected the facts and taught us to use great accuracy in the
determination of characteristics for all the orders, gave us the following
distribution for the animals
He
distributed the known animals in six classes, on the basis of three stages or
characteristics of their organic structure.
Distribution of Animals Established by Linnaeus
|
Classes |
First Stage |
|
|
|
|
I. Mammals |
A heart with two ventricles, red blood, and warm. |
|
|
|
|
|
Second stage |
|
|
|
|
III. Amphibians (the Reptiles) |
Heart with one ventricle, red blood, and cold. |
|
|
|
|
|
Third stage |
|
|
|
|
V.
Insects |
A
cold serum (in place of blood). |
Except
for the inversion which this distribution manifests, like all the others, the four
first divisions which it presents are now definitely fixed and will always be
accepted by zoologists insofar as their position in the general series. And we
see that it is the illustrious Swedish naturalist whom we have primarily to
thank for this.
The
case is not the same with the last two divisions of the distribution under
discussion. They are poor and very badly arranged. Since they include the
greatest number of known animals and those with the most diverse
characteristics, they should be more numerous. It is therefore necessary to
reformulate them and to substitute others for them.
Linnaeus,
as we see, and the naturalists who followed him, gave so little attention to
the need to multiply the divisions among the animals with a cold serum in place
of blood (the animals without vertebrae) and those in which the characteristics
present such a great variety, that they distinguished these numerous animals in
only two classes, as follows: in insects and worms. As a result,
everything which was not considered an insect, or alternatively, all
animals without vertebrae which did not have articulated members were, without
exception, included in the class of worms. They placed the class insect
after the fish, and the class worms after
the insects. The worms therefore formed, according to this
distribution of Linnaeus, the last class of the animal kingdom.
These
two classes are still found laid out, following this order, in all the editions
of Systema naturae
published after Linnaeus. And although the essential problem of this
distribution, so far as the natural order of animals is concerned, is evident
and we cannot deny that Linnaeus’ class worms is a sort of chaos in
which things very different are found united, the authority of this scholar was
so weighty among naturalists, that no one dared to change this monstrous class worms.
Intending
to institute some useful reforms in this matter, I presented in my first course
of study the following distribution for the animals without vertebrae, which I divided,
not into two classes, but into five in the order given below:
Distribution
of Animals Without Vertebrae as Laid Out in My First
Course of Study
1. Mollusks
2. Insects
3. Worms
4. Echinoderms
5. Polyps
These
classes were made up then of some of the orders which Bruguiere
had presented in his distribution of worms, an arrangement I did not adopt, and
from the class insects, such as Linnaeus had described it.
However,
towards the middle of Year Three of the revolution (1795), when the arrival of
Cuvier in Paris directed the attention of zoologists to the organic structure
of animals.
I saw, with much satisfaction, the decisive proofs which he provided for the preeminence which must be given to the mollusks over the
insects, so far as concerns the rank which these animals must occupy in the
general series, something which I had already carried out in my classes but
which had not been viewed favorably on the part of naturalists of that capital
city.
The
change which I had made in this matter, from a sense of the inconvenience in
Linnaeus’ distribution which people followed, Cuvier endorsed perfectly through
his explanation of the most reliable facts, among which several, in truth, were
already known, but which had not yet attracted our attention in Paris.
Profiting
then from the illumination which this scholar, since his arrival, has shed on
all parts of zoology, and especially on the animals without backbones, which he
called animals with white blood, I added successively new classes to my
distribution. I was the first to institute them. But, as we are going to see,
the classes of mine which were adopted were only accepted slowly.
No
doubt, what interests authors is a matter of total
indifference to science and also to those who study the subject. Nevertheless,
there is a practical value in knowing the history of changes which the
classification of animals has undergone in the past fifteen years. Here are
those which I have effected.
To
begin with, I changed the denomination of my class of echinoderms into
that of Radiata, in order to unite in it the
jelly fish and the genera which are related to them. This class, in spite of
its utility and the necessity for it on account of the characteristics of these
animals has not yet been adopted by the naturalists.
In my
course for Year Seven (1799), I established the class crustaceans. At
that time Cuvier in his Table of Animals, page 451, still included the
crustaceans among the insects, and although this class is essentially distinct
from the insects, nonetheless, the naturalists consented to adopt it only six
or seven years afterwards.
The
following year, that is to say, in my course for Year Eight (1800), I presented
the arachnids as a special class, easy and necessary to distinguish. The
nature of its characteristics were from that time on a certain indication of an
organic structure peculiar to these animals, for it is impossible that an
organic structure perfectly suitable to the insects, who all undergo
metamorphoses, reproduce themselves only once in the course of their lives, and
have only two antennae, two faceted eyes, and six articulated limbs, could give
rise to animals which never undergo metamorphosis and which, in addition,
present different characteristics which distinguish them from the insects. A
part of this truth has since been confirmed by observation. However, this class
arachnids has not yet been admitted in any work
other than mine own.
Once
Cuvier discovered the existence of arterial and venous vessels in different
animals which people confused under the name worms with other animals
very differently structured, I immediately used the implication of this new
fact to perfect my classification. In my course for the Year Ten (1802), I
established the class annelids, a class which I placed after mollusks
and before crustaceans, something required by their acknowledged
organic structure.
In
giving a particular name to this new class, I was able to keep the ancient name
worms for the animals which had always carried it and whose organic
structure obliged me to distance them from annelids. Thus, I continued
to place worms after insects and to distinguish them from radiata and polyps, with which people
will never be authorized to unite them again.
My
class annelids published in my course and in my Researches into
Living Beings (p. 24) was around for several years without being accepted
by naturalists. Nevertheless, for about the past two years, people are starting
to recognize this class. But since people are of the opinion that they should
change its name and to bring in the name worms for it, they do not know
what to do with the creatures properly called worms, which do not have
nerves, nor a system of circulation, and in this quandary, they are reuniting
them with the class polyps, even though they are very different from
them in their organic structure.
These
examples of perfection first established in parts of a classification and later
destroyed by others and later reestablished by the
necessity and the pressure of things are not uncommon in the natural sciences.
In
fact, Linnaeus combined several plant genera which Tournefort
had previously separated, as one sees in his general polygonum,
mimosa, justicia, convallaria,
and plenty of others. And now the botanists are reestablishing
the genera which Linnaeus had destroyed.
Finally,
last year (in my course for 1807), I established among the animals without
vertebrae a new tenth class, the infusorians, because after a sufficient
examination of the known characteristics of these imperfect animals, I was convinced
that I had been wrong to include them among the polyps.
Thus,
in continuing to collect the facts gained through observation and through the
rapid progress in comparative anatomy, I instituted successively the different
classes which now make up my distribution of the animals without vertebrae.
These classes, ten in number, are arranged from the most complex to the
simplest, as is the custom, as follows:
Classes of Animals Without
Vertebrae
Mollusks
Cirrhipeds
Annelids
Crustaceans
Arachnids
Insects
Worms
Radiata
Polyps
Infusorians
I will
reveal in dealing with each of these classes that they constitute the necessary
divisions, because they are based on a consideration of the organic structure
and that, although it may be or indeed must be the case that we find in the
vicinity of the limits to the classes some races, in one way or another, half
way or intermediate between two classes, these divisions offer everything which
art can produce which is most helpful in this sort of endeavour. Thus, as long
as our main concern is an interest in science, people will not be able to do
without acknowledging them.
It
will be noticed that, by adding to these ten classes which divide the animals
without backbones the four classes recognized and fixed by Linnaeus among the
animals with vertebrae, we will have for the classification of all known
animals the fourteen following classes, which I am going once more to present
in an order opposite to the natural order.
Vertebrate
Animals
1. Mammals
2. Birds
3. Reptiles
4. Fish
Invertebrate
Animals
1. Mollusks
2. Cirrhipeds
3. Annelids
4. Crustaceans
5. Arachnids
6. Insects
7. Worms
8. Radiata
9. Polyps
10. Infusorians
Such
is the present state of the general distribution of animals, and such is the
distribution of classes which have been established among them
It
will be a matter now of examining a very important questions which appears
never to have been explored or discussed. However, the solution to it is
essential. Here it is.
Since all
the classes which are part of the animal kingdom form necessarily a series of
large groups according to the growing complexity or diminishing complexity in
their organic structure, must we, in the arrangement of this series, proceed
from the most complex to the simplest or from the simplest to the most complex?
We
will try to give the solution to this question in Chapter VIII which brings
this part of the book to a conclusion. But before that we must examine a very
remarkable fact, most worthy of our attention, which can lead us to notice the
march nature follows in giving its various productions the existence which they
enjoy. I am going to talk about the remarkable degradation which is found in
all organic structure, if one moves through the natural series of animals,
beginning with the most perfect or the most complex and moving towards the
simplest and the most imperfect.
Although
this degradation is not nor can be finely demarcated, as I will reveal, it
exists in the main groups so evidently and with a sustained consistency, even
in the variations in the path, that it depends, no doubt, on some general law
which it is important for us to discover and, consequently, to seek out.
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