on

one such plans

is

in

of

In

or

except

in of

lose sight prevalent

diates metry

sym

the bilateral

the other three,

very subordinate

structure; the plan

element

this lowest type parts which vertical axis.

all

Of

ascer

joints end into transverse rings upon each other. the Ra

Articulates,

then, that these largest divisions the animal kingdom are based, but sim ply upon the general structural idea. Striking this statement was, was

to in a

is

by

it

as

at

of

of

us

a

it

Ehrenberg also,

Invertebrates.

at a

and

later period, announced another division under two heads, those with continu ous solid nervous centre, and those with

–

scattered

But

there was

ther

nervous

swellings."

real progress these latter classifications,

ei

merely

far

to

of

or

on

so

on

a

of

or

of

of

to

of

or

Lamarck,

back

For more details upon the different sys Zoology, see Agassiz's Essay Clas sification his Contributions the Natural History the United States, Vol. on

tems

I.

either

the circulating fluids, that presence the absence

to

In

parts are here again arranged

will bring animals together whatever classify them; set features we try Aristotle, founded on that the division

in

in

the Articu but one cavity, and the parts.

on

is

dividualization

of

a

is a

try either side the body, but the body has but one cavity, and soft, concentrated mass, without distinct

based

of

of

on

to a

the Mollusks, also, the parts are arranged according bilateral symme

between systems different foundations may teach that every structural combination in cludes certain inherent necessities which

This coincidence

ma.

of

In

of

of

on

a

double internal cavity. The parts are symmetrically arranged either side the longitudinal axis the

Aristotle, under the head animals with without blood, the Enaima and Anai

us

col be

of

as

the primary divisions are concerned; for they correspond the old division

on

a

in

low, forming

in

be

the Verte column ter

minating prominent head; this umn has an arch above and an arch

lates there

not this principle, distributed the animal kingdom into two great divisions, which calls Vertebrates the truth

is a

stated

In

these plans may

the most general terms. brates there vertebral

body.

ani

in

on the

departures

principle are away from the the true affinities among

but lead

of

of

Each

do

from errors, and recognition animals.

in

been made

his classification, great fundamental

key

the

affinities among Lamarck, his contemporary, the natural

mals. recognizing

us

its

details

at

and many

but though some

of

to

tempts change improvements have

new road for study, and gave

so

Cuvier's,

it;

this division

all

of

to

every naturalist. tial There have been many criticisms

classification was opened but

a

is

built

the plan now essen

cause, his principle not fully appreciated; note

the

Whatever the

his views.

of

structure is

read the finished on which the whole

grandeur

he

on

in

of

of

to

of

a

in

strange city, who looks ler the him, exterior edifices entirely new but knows nothing the plan their internal architecture. To be able to

haps there was also some jealousy

no

like the travel

of

this,

coldly received contempora first naturalists: they could hardly grasp Cuvier's wide generalizations, and per

to

can

he is

Till

do

he

to

of

animals, number must penetrate deep enough into their organization find the secret of their internal structure.

of

certain

he

a

of

characteristic

—

features

a

to

it

no

as

of

With this new principle the basis investigation, longer enough for was the naturalist know certain amount of

features,

of

Radiates.

sphere,

ry

and

organic

bear definite relations not upon any special

It

he

structural Cuvier found the whole animal kingdom only four, which called Vertebrates, Mollusks,

is

another

these plans. conceptions

by

to

at

of

in or or

true relations with other animals taining whether they were built

end

movable

of

that animals

a

was found

whose affinities had been questionable before were now once referred their

the longitudinal axis, but these animals the whole body divided from side

to

it

to

its

The value of this principle was soon application tested by facts already

known, and

[January,

Study in Natural History.

of

of

as so we

Methods

an

4