Comparison of 3 files, rendered from file:/u:/diff/diff-diff.xml

c

mpare

A

d if

d

,

g

t

,

ing

organ

sm

y

As

far

I am a

l

to judg

,

af

r long

tending

to t

e subjec

,

th

condit

ns

appear to act in two ways,—directly on the whole organisation or on certain parts alone, and indirectly by affecting the reproductive system. With respect to the direct action, we must bear in mind that in every case, as Professor Weismann has lately insisted, and as I have incidentally shown in my work on 'Variation under Domestication,' there are two factors: namely, the nature of the organism, and the nature of the conditions. The former seems to be much the more important; for nearly similar variations sometimes arise under, as far as we can judge, dissimilar conditions; and, on the other hand, dissimilar variations arise under conditions which appear to be nearly uniform. The effects on the offspring are either definite or indefinite. They may be considered as definite when all or nearly all the offspring of individuals exposed to certain conditions during several generations are modified in the same manner. It is extremely difficult to come to any conclusion in regard to the extent of the changes which have been thus definitely induced. There can, however, be little doubt about many slight changes,—such as size from the amount of food, colour from the nature of the food, thickness of the skin and hair from climate, &c. Each of the endless variations which we see in the plumage of our fowls must have had some efficient cause; and if the same cause were to act uniformly during a long series of generations on many individuals, all probably would be modified in the same manner. Such facts as the complex and extraordinary out-growths which invariably follow from the insertion of a minute drop of poison by a gall-producing insect, show us what singular modifications might result in

plants from a chemical change in the nature of the sap. Indefinite

is a much more common result of changed conditions than definite variability

and

s probably played a more impor

ant pa

t in

for

ion

of ou

omestic races. We see indefinite va

ability i

nd

ess

s

igh

culia

ties

which

istinguish th

indi

idua

s

sam

species, and which cannot be accounted for by inheritance fro

eithe

parent

from some more remote

nces

or. Even strongly-marked differences occasionally appear in

g

sam

litter, and in seedlings fro

the same seed-capsule. At long intervals of time, out of millions of individuals reared in the same count

and fed

n nearly the same food, deviations of structure so strongly pronounced as to deserve to be

ll

d

arise

but

l

e

slight

All s

ch changes of structure, whether extremely sligh

or

mark

,

which

ap

r

a

ng

m

ny

ndividu

ls

ving

ogether,

s

d

d

ind

finit

s

of t

e

ditions of life on each individual organism, in nearly the same manner as a chill affects different men in an inde

it

ann

r, accordi

g

o their state of body

ons

tution, causing coughs or colds, rheumatism, or inflamm

s of various organs. With respect to what I

ve

called

i

direct a

changed conditions, namely, through

being affected, we may infer that variability is thus induced, partly from the fact of

b

xt

mely

nsi

v

, and partly from the similarity, as Kölreuter and others have remarked, between the variability which follows from the crossing

distinct species, and that which may be observed with plants and animals when reared under new or unnatural conditions. Many facts clearly show how eminently susceptible the reproductive system is to very s

ght chang

s in the surrounding conditions

k

p

in

an a

m

t fre

s

ate

, but erroneously,

.

M

disc

vere

a

a

will produc

s

giv

and elsewhere published

, which seldom produce young

to

r

s

mewha

un

s

s

organ

re

a

ily

Some naturalists have maintained that all variations are connected with the act of sexual reproduction; but this is certainly an error; for I have given in another work a

as they are called

;—that

is, of pl

ts which have suddenly produced

t

wid

l

othe

bud

n

same

T

ese

variation

, as they may be named,

s, offsets

occur

ly

are

u

.

A

single

m

ous

nds,

produced ye

f

er year

e

und

u

if

r

,

has been kn

wn

sudden

y to assum

a new character

as buds on d

tinct

tree

, gr

ing

der different conditions, have somet

es yielded nearly the same variety—f

ins

ce, buds on peach-trees producing nectarines, and buds on common roses producing moss-roses—we clearly see tha

natu

is

subord

nat

import

nc

n

tu

g

sm

ning e

form

v

riatio

;—

of not more importance than

na

ure of the spark, by w

h a ma

combustible matter is ignited, has in determining the nat

e of the

lames. Effects

f

nd of the Use or Disuse of Parts; Corre

ated Variati

n; Inheritance. Changed

bit

produce

n

inh

r

t

ffe

t

the

of

With

the

ncreased use or disuse of par

s

had

flue

; thus

s

probably

s

one

of our

s

which has been

seldom

M

e

e b

d

scuss

ed variat

Importa

t

s

p

ob

b

;

hich are entirely wh

e and

ave

ge

e

l

but it has been lately stated by Mr. Tait that this is

onfined to the males. C

jur

by ce

tain

plants, whilst dark-

escape: Professor Wyman has recentl

ommunicated to me a good illustration of this fact; on asking some farm

s in Virginia how i

was that all their pigs were black, they informed him that the pigs ate the p

t-root (Lachnanthes), which coloured their bones pink, and which caused the hoofs of all but the black

ari

ies to drop off;

nd one of the "crackers" (i.e. Virginia squatters) added, "we select the

ack members of a litter for raising, as they alon

have a g

od chance of l

vi

g

"

:

unintentionally

s

but

under

tood

are

of

s

a

ight

are

; that

only

ny

of structure often

having

ed

eal

for

h

most part

.

N

the s

me

or

i

tics

,

the

re-

;

-

,

he

on the

the increased length of the horns

variab

have

en

ef

ni

e

,

t

e s

m

in their

u

l

m

d

C

f

D

m

s

V

etie

: difficulty of dist

ui

ing

tween

Varieties and S

ecies; origin of Domestic Varieties from one or mo

Specie

sp

ci

s

u

der

the

,

but

e differences

mos

cases are less in degree. T

as

rue, for

f ma

y

and

s

, and by other competent judges as mere varieties

well

a

a

w

an

not

much

W

n

t is

xplained ho

g

nera

at

u

d

n

ture, it

b

n that

f

nd a

amount of

a

e

I

ing

alli

d

r

the whole amount of difference between the several breeds of the dog has been produced under domestication; I believe that

a

sm

part

f the difference is d

e to thei

b

ing

istinct

.

I

trongly marked races of s

ated

spe

i

,

at all

a

r

e de

cended

from a s

ngl

ild stock

and

ose

vary

not

r

wild

ti

,

and in the lake-habitations of Switzerland,

se ancient

o

even

But

on

y

h

ows

r ba

kwards

he history of civilisation, and shows that animals

domesticated at a much earlier period than has hitherto been supposed. The lake-inhabitants o

Switzerla

cultivated several kinds of wheat and barley, the pea, the poppy f

oil, and flax; and they possessed several domesticated animals. They also carried on commerc

with other nations. All this clearly shows, as Heer has remarked, that they had at this early age progressed considerably in civilisation; and this again implies a long continued previous period of less advanced civilisation, during which the domesticated animals, kept by different tribes in different di

s, might have varied and given rise to distinct races. Since the discovery of flint tools in the superficial formations of many parts of the world, all geologists believe that barbarian man existed at an enormously remote period; and we know that at the present day there is hard

i

ro

s,

as not

at

least the do

.

of mos

f

animals will probably for ever remain vague. But I may here state, that, looking to the domestic

of the whole world, I

,

aft

r a laboriou

oll

ctio

of all known

acts, c

e to the conclusion that

of

C

ani

d

æ

have been

tamed, and that their blood, in some cases mingled together, flows in the veins of our

domestic

bre

ed

s

decided

F

and stru

ture

it is almost certain

y

re

om

two

re

rogenitors,—whether or not these deserve to be called species. This conclusion, as well as that of the specific distinction between the humped and common cattle, may, indeed, be looked upon as established by the admirable rese

ch

s of Professor Rü

imeyer

e giv

b

l

g

same species. Hav

g

ept

ne

rly

English

the f

w

alive,

ing bred and crossed them, and examined their skeletons, it appears to m

alm

st

rtain that all ar

des

endants

f the

,

; and this is the conclusion of Mr. Blyth, and of others who have studied this bird in India

som

mu

h

he

evi

ence is clear

r

all

,

Great Br

ain

not

must

otherwise

breeds of the

roug

ut th

e

it

be

ed

;

for w

will

pug-dog,

get

Many cas

s a

o

r

cord,

sh

wing

the

a rac

qui

sti

c

wou

d

ry difficult

with

qui

in character

ar

s

.

, their Differences and Origin

t

;

,

,

;

-

—

the

:

,

:

in number

the

the

oo

,

n

, differ remarkably

in

,

in this case

,

would

are

the

r

they did

s

,

s

with the wild rock-pigeon

;

J

s

ar

wit

loins; b

t

s th

s

par

.

T

at the base

.

T

.

S

,

,

or more

on

are

ve

.

T

give one

out of several which I have observed:—

, which breed very true,

—and it so happens that blue varieties of barbs are so rare that I never heard of an instance in England; and the mongrels were black, brown, and mottled. I also crossed a barb with a spot, which is a white bird with a red tail and red spot on the forehead, and which notoriously breeds very true; the mongrels were dusky and mottled. I then crossed one of the mongrel barb-fantails with a mongrel barb-spot

loins

r

,

,

;

no instanc

is

n

r

ss

d

sc

ndants

ing

a

of foreign blood

t

a

e

b

ed

w

of reversion

together by

ho

who have written

the

, as

,

ly

a

y

s have been ascertained with certainty

fr

m

qu

t

species of animals

in species. F

,

and of some other domestic animals,

s co

clusion

qu

correct

ach o

t

w

uld

b

—

made

—

not having

e

a

y

—

present

certain

in most respects

—the occasional re-appearance of

black

—and lastly,

we may safely

nclu

e

r

rock-pigeon or

the wild

that,

a

that,

t

wo rac

, between them and the rock pigeon,

; so we can in some other cases,

u

not

ith all

b

d

are in each eminently variable

S

;

likewise

several

well

ly

e

since

ha

been domesticated they

d

all pro

e

nearly

L

or both from a common parent-stock,

r

Principles of

anciently followed, and their Effects

and definite

between

s

l

m

ny

have

d

th

ir

s

;

ha

been

veral

ikewi

e