system, he formed it according to a preconcerted plan, with all its
parts beautifully linked together and mutually corresponding. All
things were ordered in _measure_, and _number_, and _weight_[1129].
There was nothing deficient, nothing superfluous; but the whole in
the strictest sense "was very good[1130]," and calculated in the
highest degree to answer the purpose of its GREAT AUTHOR. I call
it a system of _Correlation_, because there is discernible in it,
in the first place, a concatenation of its parts, by which, as to
their forms and uses, objects are linked together in groups by a
chain of affinities; so that we pass from one to the other by gentle
gradations, without having to overleap any _wide_ interval. We see
also a gradual ascent from low to high, from less to more excellent.
And this leads us to another kind of relationship between natural
objects, by which, though placed in distinct groups or in a different
series, they in some sort represent and symbolize each other.
Examples of this relationship by analogy are to be found in every
kingdom of nature, and often form an ascending series from the lowest
to the highest; for, as we shall see hereafter, these resemblances
appear to maintain a certain correspondence with each other as to
their relative situations; so that, for instance, in the animal
kingdom they ascend step by step, without being linked by affinity or
having any real juxtaposition, from the lowest groups, towards man,
who stands alone at the head, or in the centre of all.--I shall say
something on each of these kinds of relationship.
I. The relation of _affinity_ may be considered as to its _series_
and _groups_. A series, of course, consists of parts either
_concatenated_ like a chain, or placed _separately_ at small
intervals from each other. It may run either in a right line, or
deviate from it in various ways. It appears to be the opinion of most
modern Physiologists, that the series of affinities in nature is a
_concatenated_ or continuous series; and that though an _hiatus_
is here and there observable, this has been caused either by the
annihilation of some original group or species in consequence of some
great convulsion of nature, or that the objects required to fill it
up are still in existence but have not yet been discovered[1131]: and
this opinion is founded on a _dictum_ of Linné, _Natura ... saltus
non facit_[1132]. If this dictum be liberally interpreted, according
to the evident meaning of the word _saltus_, few will be disposed to
object to it; since both observation and analogy combine to prove
that there must be a regular approximation of things to each other in
the works of God; and that could we see the whole according to his
original plan, we should find no _violent_ interval to break up that
approximation: but if it be contended, that in this plan there is no
difference in the juxtaposition of the nearest groups or individuals,
and never any interval between them, I think we are going further
than either observation or analogy will warrant. Were this really
and strictly the case, it seems to follow that every group or
individual species must on one side borrow half its characters from
the _preceding_ group or species, and on the other impart half to the
_succeeding_[1133]. But one of the most evident laws of creation is
_variety_; and if we survey all the works of the MOST HIGH, we shall
no where discover that kind of order and symmetry that this strict
interpretation implies. The general march of nature therefore seems
to say, that there must be _varying_ though not _violent_ intervals
in the series of beings: or in other words, some _conterminous_
species or groups have more characters in common than others.
It was the opinion of Bonnet (in this field himself a host) and many
other Naturalists, that the series of beings was not only continuous,
but _undeviating_, ascending in a _direct_ line from the lowest to
the highest[1134]. Others, finding that this theory could not be
made to accord with the actual state of things in nature, thought
that a scale of the kingdoms of nature must represent a _map_ or
_net_[1135]; thus abandoning a continuous series: and Lamarck, as
was before observed[1136], for the solution of the difficulty,
arranged Invertebrate animals in a double subramose one. Mr. W. S.
MacLeay and (without consultation nearly at the same time) Professor
Agardh, Mr. Fries, &c. have given to the learned world an opinion
which approximates more nearly to what we see in nature: viz. That
the arrangement of objects is indeed in a continuous series, but
which in its progress forms various convolutions, each of which
may be represented by a _circle_, or a series that returns into
itself[1137]. According to this opinion,--which seems the most
consistent of any yet advanced, and which reconciles facts which
upon no other plan can be reconciled,--the series of beings is
involved in the highest degree, rolling wheel within wheel _ad
infinitum_, and revolving, if I may so speak, round its centre and
summit--_man_[1138]: who, though not including in himself all that
distinguishes them, is still the great Archetype in which they
terminate, and from which they degrade on all sides.
It is by this convolving series that the various _groups_ into
which the kingdoms of nature seem resolvable are formed. We are
instructed by the highest authority that every thing was created
"after its kind;" and the common sense of mankind in all ages has
imposed classic, generic, and other names implying sections, as
well as specific ones, upon natural objects: and though many modern
Physiologists have asserted that species form the only _absolute_
division in nature; yet as all seem to allow that there are _groups_,
and many that these are represented by a circle or group returning
into itself[1139], the most absolute division in nature, we will
not contend for a term[1140]. We now come to consider these groups
themselves, and may notice them under various denominations.
It is customary to consider all the substances of which our globe
consists as divided into _three_ kingdoms,--the _Mineral_,
_Vegetable_, and _Animal_; but strictly speaking the _primary_
division is into organized and inorganized matter; the former
resolving itself into the two kingdoms last mentioned. These, like
England and Scotland of old, have their "Land Debateable;" occupied
by those _Productions moyennes_, (to use a term of Bonnet's[1141],)
which are as it were partly animal and partly vegetable. From this
territory common to both, the two kingdoms are extended in a nearly
parallel direction till they reach their extreme limits, without
any incursion from either side upon their mutual boundaries, but
each showing its kindred with the other by certain resemblances
observable between _opposite_ points; so that valley corresponds with
valley, mountain with mountain, river with river, sea with sea[1142];
not, however, so as to form an exact counterpart, but only in some
general features. But to leave metaphor;--as the vegetable kingdom
is distinguished from the mineral by its organization and life, by
its circulation of sap, and by its powers of reproduction by seed
or otherwise; so is the animal from the vegetable by its powers of
volition and locomotion[1143], by its nervous systems and organs of
sensation, and the senses to which they minister, by its muscular
irritability, and by its instinctive endowments.
Having made these observations with regard to the primary division
of natural objects in general,--what I have further to say will be
confined to the _animal_ kingdom, and ultimately to the branch of
which we are treating.
i. Lamarck divided the animal kingdom into two _provinces_, or
_subkingdoms_ as they are now called; the one consisting of all those
animals whose skeleton is _internal_ and built upon a vertebral
column, which are denominated _Vertebrates_; and the second, of those
whose skeleton or its representative is for the most part _external_,
including the muscles,--these are called _Invertebrates_[1144].
Though this distinction is so marked as in general to form a most
striking characteristic, yet when these two provinces approach
each other, it begins to disappear. Thus the vertebral column,
forming one piece with the shell[1145], becomes almost _external_
in the Chelonian reptiles, or tortoises and turtles, and almost
disappears in the cyclostomous fishes; and there is the beginning
of an _internal_ one in the _Cephalopoda_, or cuttle-fish belonging
to the Invertebrates. Dr. Virey, assuming the nervous system as his
basis, long since divided the animal kingdom, without assigning
names to them, into _three_ subkingdoms[1146]; M. Cuvier has
_four_--_Vertebrata_; _Mollusca_; _Articulata_; _Radiata_[1147]:
and Mr. MacLeay, finding _five_ variations of that system, divides
animals into _five_ provinces or subkingdoms, of which I formerly
gave you some account[1148];--viz. _Vertebrata_, in which the
nervous system has only one principal centre; _Annulosa_, in which
it is ganglionic, with the ganglions arranged in a series, with a
double spinal chord; _Mollusca_, in which it is ganglionic, with the
ganglions dispersed irregularly but connected by nervous threads;
_Radiata_, in which it is _filamentous_, with the nervous threads
radiating from the mouth; and _Acrita_, in which this system is
_molecular_[1149]. And to this division of the kingdom, as founded on
a satisfactory basis, I should recommend you to adhere: still however
we may speak of vertebrate and invertebrate animals, as forming the
_primary_ subdivision of them, taken from a striking character and
obvious to every one who sees them.
If you inquire into the rank of each of these subkingdoms, of course
you will assign the principal station to the _Vertebrates_, which
are the most perfectly organized, to which _man_ belongs, and over
which he immediately presides. If we form the scale according to
the nervous system of each province, that in which the organ of
sensation and intellect is most concentrated will stand first; and
in proportion as this organ is multiplied and dispersed will be the
station of the rest, which will place them in the order in which I
have mentioned them; and the _Annulosa_, to which insects belong,
will precede the _Mollusca_, which Cuvier and Lamarck had placed
before them on account of their system of circulation. But when
we reflect that a _heart_ and _circulation_ occur in some of the
conglomerate _Polypi_[1150], animals that approach the _vegetable_
kingdom; that some of the acephalous _Mollusca_ have no visible
organs of sense, except that of taste, whose substance is little
better than a homogeneous gelatinous pulp, and who seem from their
inert nature to have very slight powers of voluntary motion[1151], we
shall be convinced that a heart and circulation alone, unaccompanied
by a more concentrated nervous system and more perfect structure,
cannot place an animal above those which in every other respect so
obviously excel them. With regard to _insects_ particularly, we may
further ask--Who that considers how man employs his powers and organs
even in his most degraded state, or that contemplates the wonderful
works that he is enabled to accomplish when his faculties receive
their due cultivation and direction, can avoid regarding him as
superior to the rest of the animal creation? And what unsophisticated
mind, not entangled in the trammels of system, when it surveys the
industry, the various proceedings, and almost miraculous works that
have been laid before you, the waxen palaces of the bee,--the paper
cottages of the wasp and hornet,--the crowded metropolis of the
white ants,--the arts, the manufactures, and stratagems of other
insects,--the associations and labours for the common good of those
that are gregarious;--will not at once conclude that they must be a
superior race to the slug, the snail, and others, which live only to
eat and propagate their kind?
Or who, that considers the wonderful structure of the animals whose
cause I advocate,--the analogy that exists between their organs of
manducation, of motion, and of sensation, and between various other
parts of it[1152], with those of the higher animals,--the acuteness
of their senses, their wonderful strength of muscle[1153], and
powers of locomotion[1154],--but will think them superior to the
headless and almost inanimate oyster or muscle, or the conglomerate
_Alcyonia_, though they have a heart and circulation?
Who again, that observes that in proportion as pedate animals
approach to the human type, their motions are accomplished by fewer
organs,--that man walks _ore sublimi_ upon _two_ legs; the majority
of quadrupeds upon _four_; insects upon _six_: the _Arachnida_
apparently upon _eight_; most _Crustacea_ upon _ten_; and the
_Myriapods_ and others upon _many_,--but will thence conclude that
insects must precede the _Arachnida_ and _Crustacea_?
Who, once more, that reflects that if any of the superior animals are
deprived of a limb it can never be reproduced, and that in insects
the same circumstance occurs; while spiders and _Crustacea_ if they
lose a leg have the power of reproducing it, and the _Mollusca_ if
they are decapitated can gain a new head,--will consent to their
being placed after any of these animals[1155]?
Lastly, who that recollects that the _Mollusca_ are hermaphrodites,
like most plants, bearing both male and female organs in the same
body,--but will allow that insects, in which the sexes are separate as
in the Vertebrates, must be more perfect, and of a higher grade[1156]?
ii. We now come to the _Classes_ into which the _Annulosa_ are divided.
This term appears first to have been employed by Tournefort, and was
adopted by Linné[1157]. As the nervous system of animals furnishes
the most prominent distinction of a subkingdom, so the _circulation_
of their fluids, and their _respiration_ necessarily connected with
it, seems best to point out the _classes_ into which it may next be
resolved. But having fully explained my ideas on this subject in a
former letter, I need not here repeat what I then said[1158].
iii. As we have subkingdoms, so we may also have _subclasses_,
or such large divisions of a class--not founded upon internal
organization or any of the primary vital functions, but upon
different modes of taking their food, or such other _secondary_
characters--as include more than one _Order_. To this description
Clairville's _Mandibulata_ and _Haustellata_ appear to me to belong,
which I think are by no means entitled to the rank of Classes; for
whoever compares these two tribes together will at the first glance
be convinced, by the numerous characters they possess in common,
notwithstanding the different mode in which they take their food,
that they form one connected primary group. This circumstance,
therefore, only furnishes a clue for their further subdivision into
two secondary groups, separated by distinctions certainly of a lower
value than those which separate the _Crustacea_ and _Arachnida_ from
_Insecta_. This is further confirmed by the variations that take
place in their mode of feeding in their different states; some from
masticators becoming suctorious (_Lepidoptera_), and others from
being suctorious becoming masticators (_Myrmeleon_, _Dytiscus_,
&c.),--which shows that this character does not enter the essential
idea of the animal.
iv. Next to Classes and Subclasses we are to consider those groups
of insects that are denominated _Orders_. The characters of these at
first were taken principally from the instruments of flight or the
absence of them; and the name appropriated to each Order by Linné,
after Aristotle, had reference to this circumstance. But this alone
does not afford characters sufficiently discriminating: for though
to an accurate observer a difference in these organs appears to be
characteristic of most of the Orders, yet in some it is not easily
detected or defined. In the _Neuroptera_ there are as many different
types of wings as there are of tribes or suborders. So that it
seems not possible so to construct the definition of every Order,
as to take its character from the organs of flight alone. Linné was
sensible of this, and was compelled to have recourse to subsidiary
characters in the majority of his: his observation therefore with
regard to _Genera_,--that the character does not give the genus, but
the genus the character[1159],--applies equally to _Orders_; and the
characters included in the definition of an Order, should be the
result of a careful examination of its component groups.
On a former occasion I named to you the Orders into which it
appeared to me the Class _Insecta_ might be divided[1160]; they were
these. _Coleoptera_; _Strepsiptera_; _Dermaptera_; _Orthoptera_;
_Hemiptera_; _Trichoptera_; _Lepidoptera_; _Neuroptera_;
_Hymenoptera_; _Diptera_: _Aphaniptera_; _Aptera_. I then briefly
explained them merely for the sake of illustration, and that you
might know what description of insects were meant when these Orders
were mentioned in my letters, without intending to affirm that I had
arranged them in a natural series, or that all of them were perfectly
natural. I shall now consider them separately, and conclude with
giving my sentiments as to which should be placed first.
* _ORDERS in which the ordinary Trophi all occur, or the_
Mouth _is_ perfect[1161]. (_Mandibulata._)
1. COLEOPTERA[1162] (_Eleutherata_ F.). Aristotle may be called the
founder of this Order, since he both named and defined it[1163].
Both his name and definition were adopted by Linné; and the former
(with the exception of Fabricius and his school) by all succeeding
Entomologists. To his definition _Wings in a sheath_[1164], other
characters have been added; as the folding of the wings, and the
straight suture by which the elytra are united[1165]. Aristotle's
character, though to be found in the great majority of the Order,
is not universal, since there are some beetles that have neither
wings nor sheath, as the female glow-worm; and many that though
they have the sheath have no wings, as _Meloe_, many _Carabi_, &c.
To the transverse folding of the wings there are also exceptions;
as in _Buprestis_, _Molorchus_, &c. The straight suture by which
one elytrum exactly coincides with the other without lapping
over, fails in _Meloe_: so that no one of these characters can be
called universal in the Order; but as an exception or two does not
invalidate a rule, and these are sufficiently universal for the
purpose of pointing it out, they may be retained. Perhaps it will be
an improvement to add the kind of the _metamorphosis_, which, as far
as known, prevails universally.
DEF. _Metamorphosis_ incomplete[1166].
_Legs_ inosculating, posterior coxæ usually transverse.
_Elytra_ corneous, or coriaceous, without veins, united
by a straight suture, so as mostly to cover the wings
completely[1167].
_Wings_ longitudinally and transversely folded[1168]:
_neuration_ simple[1169].
2. STREPSIPTERA[1170] (_Rhiphiptera_ Latr.) The characters of this
Order were first given in the _Linnean Transactions_, and it has been
adopted by Latreille, who however, without sufficient reason, has
changed the name originally imposed to _Rhiphiptera_[1171]. Rossi,
who was the first that discovered an insect of this Order, concluded
that because it was parasitic it must be _Hymenopterous_; and it is
certainly more nearly related to that Order than to the _Diptera_,
amongst which M. Lamarck has arranged it, and with which it has no
character in common, except having two wings. This is one of those
Orders, consisting of few genera and species, which, from their
connecting two circles, Mr. MacLeay has called _osculant_, who places
it between the _Hymenoptera_ and _Coleoptera_[1172].
DEF. _Metamorphosis_ subincomplete[1173]?
_Pseudelytra_ twisted, attached to the anterior leg[1174].
_Wings_ not covered by the elytra, longitudinally folded,
forming nearly the quadrant of a circle[1175]: _neuration_
simple.
_Anus_ styliferous[1176].
3. DERMAPTERA[1177] (_Ulonota_ F. _Orthoptera_ Oliv.). This is
another osculant Order, evidently connecting the _Coleoptera_ with
the _Orthoptera_. The elytra are of a coriaceous substance, have
a straight suture, and are not veined, and the wings are folded
longitudinally as well as transversely,--circumstances which connect
it with the former Order,--while the shape of its wings, its oral
organs, and its metamorphosis, show its affinity to the latter.
It was established at the same time and in the same work with the
preceding Order, in pursuance of a suggestion of Dr. Leach, and
consists solely of the Linnean genus _Forficula_.
DEF. _Metamorphosis_ semicomplete.
_Elytra_ coriaceous, without veins, united by a straight
suture, so as partly to cover the wings.
_Wings_ longitudinally and transversely folded, each forming
nearly the quadrant of a circle: _neuration_ radiating[1178].
_Anus_ forcipate.
4. ORTHOPTERA[1179] (_Ulonota_ F.). This Order, which Linné at first
regarded as belonging to the _Coleoptera_[1180], and afterwards
improperly added to the suctorious _Hemiptera_, was very judiciously
separated from both by De Geer, under the name of _Dermaptera_,
a name not improper, and which ought to have been retained. Its
present name was, I believe, assigned to it by Olivier; and as this
is generally in use, I shall not attempt to disturb it. Dr. Leach
divided the Order into two, separating the _Blattina_ from it, under
the name of _Dictyoptera_[1181]. He was led to this by the tegmina
decussating or lapping obliquely over each other, whereas in the
rest the horizontal portion of one tegmen lies longitudinally over
that of the other; he also probably took their depressed body into
consideration;--these circumstances, however, rather indicate a
_tribe_ or suborder; and as such Mr. MacLeay regards it.
DEF. _Metamorphosis_ semicomplete.
_Legs_ suspended.
_Tegmina_ generally pergameneous[1182], reticulated with
nervures, more or less incumbent, covering the wings.
_Wings_ longitudinally folded, ample: _neuration_ reticulated.
5. NEUROPTERA[1183] (_Synistata_, _Odonota_ F.). Of all the Linnean
Orders this appears to consist of the most discordant tribes; so
that it seems next to impossible to construct a definition that
will include them all, unless indeed we admit M. Latreille's idea,
adopted by Mr. MacLeay[1184], that a varied metamorphosis is its
essential character; or, to speak more largely, variety itself
seems the characteristic of the insects composing it, in every
state; and there is scarcely a common distinctive character in their
perfect state, upon detecting which in any individual you may
exclaim--This is a Neuropterous insect. The only one that I have
been enabled to seize is, that their _scapulæ_ and _parapleuræ_
are parallel and placed obliquely[1185]. Whether, with all this
puzzling variation and dissonance between the different tribes of
which it is now composed, this Order can be considered as a natural
group, in the present state of our knowledge it would be rash to
decide. I shall observe, however, that the _Libellulina_,--whether
we regard their metamorphosis and the singular character before
described that distinguishes their larva and pupa[1186], their oral
instruments[1187], the remarkable position of their legs[1188], their
general form, the wonderful and peculiar machinery by which their
wings are moved[1189], and other circumstances of their internal
anatomy,--if any are to be regarded as forming a separate Order, are
the first entitled to that distinction. At present, with our friend
Mr. MacLeay, I shall consider it as not further divisible, and as
consisting of five principal forms. I must not omit to observe, that
in the _Ephemerina_ the parts of the mouth, except the labrum and
palpi, appear to be mere rudiments[1190].
DEF. _Metamorphosis_ varying. _Larva_ a hexapod.
_Wings_ four in most, and reticulated with numerous areolets.
_Prothorax_ distinct.
_Scapulæ_ and _Parapleuræ_ parallel and oblique.