“Then, again, the ovaries and testes do not exhibit a

corresponding segmentation. When it is allowable to speak of

ovary or testis at all as in _Lumbricus_, we find that in

the case of both organs we have at most two pairs.”

It seems to me that the distribution of the generative organs in

a comparatively-developed member of the Annelid type, is not the

question. We have to ask what it is in undeveloped members of that

type. Among them the repetition of generative parts is in some cases

just what the theory implies. Thus in Claus I read:--“In the marine

_Chætopoda_, the ova or spermatozoa originate on the body-wall from

cells of the peritoneal membrane, either in the anterior segments

alone or along the whole length of the body.” So that in these last

cases there are, in all the segments, parts from which arise generative

products. The fact that these parts are not definite ovaries and testes

is irrelevant. Ovaries and testes are developed generative structures,

and in the order of evolution are preceded by undeveloped ones; and the

fact that these undeveloped ones are found in little-developed members

of the type conforms perfectly to the hypothesis. [I may remark in

passing that here is a good illustration of that process of evolution

which, in the above speculation of Prof. Korschelt, is supposed to be

inverted: many dispersed, similar, and indefinite parts, are integrated

into a few localized and definite parts.]

In continuation the critic above quoted says:--“My position is that

the repetition of segments in an Annelid is a phenomenon of the same

nature as the repetition of hairs in a Mammal or of scutes in a

Reptile”, and he proceeds to give instances of repetitions of organs

in other types, as of the reproductive structures and excretory

system in the young Dog-fish or of the ovaries in _Amphioxus_. These

examples do not seem to me relevant. No parallelism exists between

the repetition of a particular organ in an animal, and the repetition

of an entire cluster of organs constituting a physiological whole.

The repetitions of the ovaries in _Amphioxus_ and of the excretory

system in a young Dog-fish, occur without threatening to divide into

similar parts the entire organism. But the segmental repetitions in

an annulose creature implicate the structures at large, and would, if

pushed a little further, result in separate creatures. The segment

of a low Annelid contains alimentary, vascular, nervous, excretory,

reproductive, sensory and locomotive organs--all the organs required

for carrying on life, save certain organs of external relation which

its position excludes. When there is shown some vertebrate animal, or

proto-vertebrate animal, that is divisible into parts each of which is

in great measure physiologically independent, I shall feel obliged to

abandon my position.

* * * * *

While this appendix is in hand I have received from another expert,

whose view is in general agreement with my own, a letter containing the

following passage:--

“You will see that Dohrn’s theory was the antithesis of your

own view of vertebrate structure, namely that the vertebræ

were formed by the segmentation, from mechanical causes of a

body originally simple. This view of yours has been confirmed

by later researches, which have shown that the most primitive

forms allied to the Vertebrates, possessing the essential

organs, viz., gill-slits, notochord, and dorsal nerve cord,

are not segmented animals, like Annelids and _Crustacea_, but

simple animals, having at most three regions, not exactly

corresponding to segments. These primitive unsegmented forms are

Ascidian tadpoles, _Balanoglossus_, and certain other primitive

forms. The embryology of Vertebrates also proves that they are

originally simple and not segmented animals, especially the

fact that there is originally one pronephric duct or primitive

kidney.”

Nevertheless there survives a leaning towards the notion of a segmental

origin of the _Vertebrata_. But the repetitions of organs named in

support of this notion have, I think, no more relation to the genesis

of the vertebrate type than the multiplication of vertebræ in a snake

has relation to the genesis of the vertebral column.

APPENDIX E.

THE SHAPES AND ARRANGEMENTS OF FLOWERS.

In Part IV., Chapter X., under the title of “The Shapes of Flowers,” I

have, after describing their several kinds of symmetry, as habitually

related to their positions, made some remarks by way of interpretation.

The truth that flowers exhibit a radial symmetry when they are so

placed as to be equally affected all round by incident forces, having

been exemplified, and also the truth that they assume a bilateral

symmetry when they are so placed that their two sides are conditioned

in ways different from the ways in which their upper and lower

parts are conditioned; I have gone on to inquire (in § 234) by what

causes such modifications of form are produced. I have stated that,

originally, I inclined to ascribe them entirely to differences in the

relations of the parts to physical forces--light, heat, gravitation,

etc.; but that I found sundry facts stood in the way of this

interpretation. And I have said that “Mr. Darwin’s investigations into

the fertilization of Orchids led me to take into account an unnoticed

agency.” Continuing to recognize the physical forces as factors having

some influence, I have concluded that the most important factor is

the action of insects; which, aiding most the fertilization of those

flowers which most facilitate their entrance, produce, in course of

generations, a form of flower specially adapted to the special position.

Though still adhering to this interpretation, I have since found reason

to think that the original interpretation contains a larger portion

of truth than I supposed at the time when I was led thus to revise

it. While staying at Mürren, in Switzerland, in 1872, I observed

some modifications in a species of Gentian, which proved to me that

the action of incident physical forces on flowers is, in some cases,

very rapid and decided. The species furnishing this evidence was the

_Gentiana Asclepiadea_; which I found in a copse formed of bushes

that were here wide apart and there close together. In some places not

near to the bushes, the individuals of the species grew vertically; in

other places, partially shaded, their inclined shoots curved in such

directions as to get the most light; and in other cases their shoots

were led to take directions almost or quite horizontal. That, along

with these modifications in the directions of their shoots, there went

adjustments in the attitudes of their leaves, was a fact not specially

worthy of remark; for plants placed inside the windows of houses

habitually show us that leaves quickly bend themselves into attitudes

giving them the greatest amounts of light. But the fact which attracted

my attention was, that the flowers changed their attitudes in an

equally-marked manner. The radial distribution passed into a bilateral

distribution with the greatest readiness. Comparison of the annexed

figures will show the character of this change.

Figure I. represents part of a vertically-growing shoot. This

belonged to an individual growing unimpeded by bushes, and getting

light on all sides. Here it is observable that the pairs of leaves,

placed alternately in directions transverse to one another--one pair

pointing, say, north and south, and the next pair pointing east and

west--maintain, taking them in the aggregate, a radial distribution;

and it is also observable that the alternate pairs of flowers are

similarly arranged.

Figure II. is a sketch from a shoot which leaned towards one side,

and of which the higher part, as it bent more and more, got its upper

side more and more differently conditioned from its lower side. Here

we find that not only the leaves, but also the flowers, have adjusted

themselves to the changed conditions. The leaves of the lowest pair

hang out in the normal way, on the opposite sides of the axis, so that

a plane passing through their surfaces will cut the axis transversely;

and their two axillary flower-buds, _c_ and _d_, are similarly placed

on opposite sides of the axis. But at the other part of the shoot, we

see both that the leaves have adjusted themselves so that their planes,

no longer cutting the axis transversely, keep a fit adjustment with

respect to the light; and also that the flowers, no longer on opposite

sides of the axis, have bent round to the upper side, as at _a_ and _b_.

Figure III. shows us this re-arrangement carried still further. The

shoot it represents was growing in a direction nearly horizontal, and

therefore receiving the light only on one side. And here, besides

seeing that the leaves have so adjusted themselves that they all lie in

approximately the same plane, which is parallel to the axis instead of

transverse to it, we see that the two pairs of flower-buds have both

come round to the upper side of the axis. So that in this shoot, the

original radial symmetry in the arrangement of leaves and flowers, is

completely changed into a bilateral symmetry.

[Illustration: Figs. 1–3.]

These facts do not, it is true, prove any modification in the forms

of the flowers themselves: they only prove modification in the grouping

of the flowers. But beyond showing, as they do conclusively, how

readily a bilateral arrangement of flowers is producible out of an

arrangement that was not bilateral, by the action of light, etc.;

they give increased probability to the belief that changes in the

shapes of flowers are producible by the same agencies. Doubtless this

change in the attitudes of the flower-buds is due to the action of

light on their calyces and peduncles more than to its action on their

unfolding corollas. But along with an action so decided on the growth

of these sheathing and supporting organs containing chlorophyll, it

is scarcely probable that there is _no_ action on the growth of the

petals, containing other colouring matter; considering that in both

cases the development of the colouring matter depends on the action of

light, and considering also the effect of light on petals, familiarly

shown by their opening and closing. And if even but a small effect is

producible on the growth of the corolla, then it is to be expected that

light will be an agent in changing the form of the corolla, when the

attitude of the flower causes its parts to be differently exposed. For

a small effect on the individual flower will become a great effect in

the flowers of remote descendants; provided the changed attitudes of

the flowers preserve considerable constancy throughout the succession

of individuals.

Be this as it may, however, the facts I have here described, which

I doubt not other observers have seen paralleled in other plants,

are instructive, as showing how quickly certain metamorphoses are

produced, and as implying the easy establishment of such metamorphoses

as permanent characters in a species, if the modifying conditions

become permanent. The changes of arrangement I have pointed out, do not

become permanent in this species because its individuals are variously

affected by the modifying forces: on some they do not act at all,

on some a little, on some much; and even on the same individual the

different shoots are quite differently affected. But if the habit of

this plant were greatly changed--if, for instance, by spreading into

habitats yielding abundant nutriment, the plant became very luxuriant,

and, multiplying its branches, grew shrub-like; it is clear that, being

shaded by one another, these branches would be habitually circumstanced

in a way like that which we here see produces bilateralness in the

distribution of the flowers, if not in the flowers themselves; and

being thus permanently affected, would become permanently bilateral.

Accumulating by inheritance, what is here only an individual

peculiarity, would become a peculiarity of the species--a specific

character.

APPENDIX F.

PHYSIOLOGICAL (OR CONSTITUTIONAL) UNITS.

There has recently come before me a fact which has a significant

bearing on the hypothesis of Constitutional units: serving, indeed, to

give an apparently conclusive proof of its truth. Before stating it,

however, I may with advantage re-state the several evidences already

assigned in support of it.

* * * * *

1. First comes the _à priori_ reason. These units in the germ of an

organism which cause development into a special structure, cannot be

_chemical_ units--cannot be simply molecules of proteid substance in

one or other of its forms; since these are not special to any type of

creature but common to all creatures. Nor can they be what we may call

_morphological_ units--the cells or protoplasts; because in the early

stages of development the cells of one organism are indistinguishable

from those of others, and because were cells the units of composition

there could be no interpretation of what are called unicellular

organisms--nothing to account for the innumerable varieties of them.

Hence, of necessity, the structural elements of which each organism is

built, being neither proteid molecules nor cells, must be something

between them: probably some complex combination of different isomeric

forms of proteids.

* * * * *

2. That units of such natures are the essential components of each

species of organism, is shown by the fact that in low types of

creatures, little differentiated into special tissues, any considerable

portion of the body will, when separated, begin to assume the structure

proper to the species--a truth recently shown afresh by Prof. T.

H. Morgan’s experiments on the regeneration of _Planaria maculata_

(already referred to in § 206) showing that various fragments cut out

develop into new individuals, and that when, being too small they die

before doing this, there is always an abortive attempt to assume the

specific structure.

* * * * *

3. This truth that a portion of undifferentiated tissue, if adequate in

quantity, assumes the structure of the type, illustrating as it does

the proclivity of the constitutional units towards the structure of

the species, allies itself with the phenomena of both agamogenesis and

gamogenesis. The first of these shows us how a fissiparously-detached

portion of the parental tissue takes on the same form as the parent;

and the second shows how those small detached portions distinguished

as sperm-cell and germ-cell also, when united and supplied with the

needful materials, do the same thing.

* * * * *

4. But the set of phenomena following the union of sperm-cell and

germ-cell differ in a certain way from those which follow when a

_gemma_ or other unfertilized portion of parental tissue is detached.

The incomprehensibleness of this difference as otherwise contemplated,

and the partial comprehensibleness of it when joined with the

hypothesis of physiological units, furnish a further support for the

hypothesis.

The familiar truth learnt by the tyro in algebra that an apparent

solution which contains the unknown quantity is no solution, is a

truth apt to be overlooked in other spheres than the algebraic. An

illustration is supplied by the answer once given in Parliament to the

question “What is an Archdeacon?”--“One who discharges archidiaconal

functions.” But science as well as daily life furnishes examples.

When it is said by Engelmann, Hensen, Hertwig, and Maupas that “the

essential end of sexuality is rejuvenescence, that is, the restoration

of growth-energy,” we have another instance of an explanation which

explains nothing. What is the phenomenon to be explained? That

unfolding of an organism from a germ which displays growth-energy. And

what is the explanation? The giving of fresh growth-energy. The unknown

quantity “growth-energy” is contained in the explanation proposed.

There exists no conception of “juvenescence” save that derived from

observing developing plants and animals; and if “re” be prefixed, no

interpretation is thereby given to the unexplained thing “juvenescence.”

Coleridge somewhere comments on a source of fallacy which he calls the

“hypostasis of a relation”--the changing of a relation into a thing.

The plumber who tells you that water rises in a pump “by suction”

supplies an instance. Having assumed suction to be an agent, he

thinks that he understands how the piston does its work. Some of the

explanations given of fertilization supply further instances. When it

is said that sexual union has for its end “to give increased vigour

to all the vital processes,” it is tacitly implied that vigour is a

something--a something which can be given. But now, in the first place,

it is only by the hypostasis of a relation that we are led to think

of vigour as a thing. Vigour is a state--that state of a living body

which enables it to give out much motion. What enables it to do this?

The presence in it of abundant molecules containing much molecular

motion which can be transformed into molar motion: the transformation

being effected by the falling of these molecules into their simpler

and relatively-inert components, which are thereupon excreted.

Energy-containing matter is used up, and more energy or vigour can be

given only by supplying more such matter. How then can the union of

two nuclei--those of the sperm-cell and germ-cell--give vigour? Only

an infinitesimal portion of vigour in the sense above explained exists

in either, and the union of them leaves it still infinitesimal. And

then, even supposing the vigour to be an entity and to be appreciable

in quantity, how could it go on producing that immense combination

of physiological actions seen in the unfolding of the germ into an

organism? and how could it go on producing the physiological actions of

an adult organism during a whole century?

May we not then say that these proposed explanations leave the question

where it was--are nominal solutions, not real solutions?

* * * * *

5. But the hypothesis of constitutional units furnishes, if not a

satisfactory answer yet, something in the nature of an answer--a true

cause; that is to say, a cause actually known to us as operating in

other cases. In § 92 it was pointed out that in proportion as units

are similar, there may be built up from them an aggregate which is

relatively stable, and that along with increasing dissimilarity the

stability of the aggregate decreases. It was inferred that if a group

of constitutional units belonging to one individual which have become

moulded into relatively exact congruity with the organism and with

one another by long co-operation, are mingled with some belonging

to another individual which, differently circumstanced, has become

somewhat different in itself and in its units, then the mass formed by

the union of the two groups will be relatively unstable--relatively

modifiable by incident forces. Whereas in either organism, no longer

perpetually changed in the relations of its parts by growth, there is

an approach towards equilibrium between the whole and its components,

the components contributed by the two to form a germ, being slightly

unlike one another, will not form a group in a state of equilibrium.

The group they form will be capable of easy change by incident forces;

and they will so be rendered free to follow their proclivities towards

the typical form of the species. Inferring this we must also infer that

so long as these two sets of slightly different units are not exposed

to any constant forces tending to coerce them into the same form, there

will continue to exist in the nuclei of all descendant cells this same

relative instability and consequent plasticity.

Such evidence as we have verifies this interpretation. There is

first the universal fact that development of the germ begins when

it is exposed to an incident force--heat--the undulations of which,

increasing the oscillations of the mixed units, give them greater

freedom to arrange themselves in conformity with their type. We see

this alike when spring warmth makes a seed germinate and when the

warmth of a sitting hen sets up organization in her eggs. Heat frees

the molecules of inorganic matter from local restraints and, as we see

in molten metal, lets them yield to other forces; and similarly in this

organic matter, the units are made free to follow their proclivities.

Then, secondly, there comes the evidence from comparisons between the

effects of mixing constitutional units differing in various degrees.

Let the cluster of mixed units be derived from animals that are

ordinally distinct. Nothing happens. The units each contributes tend to

arrange themselves after the parental type. Hence a conflict between

the tendencies towards two markedly unlike structures, and no structure

arises. Suppose the mixed units come from two kindred species--say

horse and ass. The structures which they respectively tend to form,

being in their main characters alike, there is such co-operation

as produces a working organism but an organism in certain respects

imperfect--a mule. Suppose, again, the units come from two varieties

of the same species. A perfect organism results, and, as shown by Mr.

Darwin when detailing the effects of crossing, an unusually vigorous

organism. The units being more unlike than those belonging to the same

variety, the instability of the germ-plasm is unusually great, and

the transformations which constitute development and action become

unusually active. When, as in ordinary cases, the units are supplied by

members of the same variety who have not been made very much alike by

their antecedents, there follows the usual amount of organic vigour.

Coming now to the results of breeding in-and-in--breeding between

individuals whose constitutions (_i.e._ constitutional units) have for

generations been growing more alike in the absence of crossing with

other stirps--we see that diminution of organic vigour is displayed:

there is a decrease in the rate of physiological change. Finally, on

coming to a closer relationship, as in marriages between cousins, in

whom the constitutional units are more than commonly alike, we see

there frequently follows either barrenness or the production of feeble

offspring.

All these facts, then, are congruous with the hypothesis that the

use of fertilization is the mixing of unlike units, and consequent

production of plasticity. Leaving out cases in which the unlikenesses

are so great as wholly to prevent co-operation among the units, the

degree of vigour, that is, the activity of physiological change, is

great where the unlikeness is great and diminishes with the approach

towards likeness.

* * * * *

6. The existence of constitutional units seems otherwise necessarily

implied. I refer to the fact that no organism is a homogeneous mean

between its parents but consists of a mixture of parts, some following

one parent and some the other. Among illustrations of this the most

conspicuous are those yielded by the variously-mixed colours of

hair or feathers. Horses, cattle, dogs, cats, hens, pigeons display

these mixtures: colours in one place like the mother and in another

place like the father. As the internal organs are invisible, and as

visible organs have indefinite shapes and graduate indefinitely into

adjacent ones, the mixture of traits is elsewhere less conspicuous; but

occasional marked cases (especially in malformations) leave no doubt

that it pervades the entire organism.

This peculiarity of transmission seems necessarily to imply that there

are distinct units derived from the two parents, and that in the course

of development there is more or less segregation of them--those of

the one origin predominating so far in some places as to give special

likeness to one parent, and those derived from the other doing the like

in other places. All which interpretation is impossible unless the

hypothesis of constitutional units be admitted.

* * * * *

7. I come at length to the special evidence referred to at the outset.

It is evidence of the same nature as that just assigned, but carried

to a higher stage. It is furnished not by the segregation of traits

derived from two parents of the same variety, but is furnished by the

segregation of traits derived from parents of different varieties. In

articles on “Bud Variations or Sports” (_Gardener’s Chronicle_, 1891)

Dr. Masters gives various examples of the separation or unmixing of

ancestral constitutions. Mr. Noble formed a hybrid between _Clematis

Jackmani_ and _C. patens_. One of these varieties flowers in the autumn

on new wood, while the other flowers in the spring on old wood; and

the result is that flowers of two kinds, quite unlike, are produced at

different parts of the year, and that by pruning so as to cut away one

or other set of shoots, the plant may be made to produce exclusively

for the time being one or other sort of flower.

“Another very interesting case of unmixing, or, if it be

preferred, of partial mixture, is afforded by Neubert’s

Berberis. This is a hybrid between the evergreen pinnate-leaved

Mahonia and the deciduous simple-leaved Berberis vulgaris, and

it bears leaves some of which are intermediate in appearance,

while others are much like those of one or other of its parents.

“A not uncommon illustration of a similar kind, is the

production of a Peach and a Nectarine on the same branch, and we

have just learnt from Canon Ellacombe that some of the Berlin

Hellebores show evidence of their hybrid nature by occasionally

producing foliage [and flowers?] of the two parents separately

from the same root-stock.

“In addition to the cases given above, we may here cite a few

more which have come under our notice, such as a Chrysanthemum,

half the florets of which are of one colour, half of another.

A hybrid Calanthe, showing a similar piebald variation, is

shown in Fig. 14. A very curious case was that of the Narcissus

received from Mr. Walker, and in which flowers of two distinct

varieties sprang from the same bulb. Grapes not uncommonly show

their crossed origin by presenting a striped appearance, one

stripe being of one colour, one of another, as may also be seen

in the Orange, Apple, Lemon, and Currant.”

Thus, however the germ-plasm is constituted its essential components

cannot be all alike. Before there can be this dissociation of ancestral

characters, there must be in the germ-plasm different elements capable

of being dissociated. This single fact seems to compel us to assume

constitutional units.

APPENDIX G.

THE INHERITANCE OF FUNCTIONALLY-CAUSED MODIFICATIONS.

In Part II, Chapter X^A, I have confessed that the process by which

a structure changed by use or disuse affects the sperm-cells or

germ-cells whence arise descendants, is unimaginable: without, however,

inferring that therefore such a process does not exist. With others

it seems different. Some three years ago the following expression of

opinion came to me from a zoological expert:--

“Many zoologists--most of us here at Cambridge--are intensely

opposed to the doctrine of the inheritability of acquired

variations. Even assuming that the developmental power of a

germ is determined by its molecular structure (and I for one

would question this--Driesch and his school when they find that

they can squeeze a developing egg into all sorts of shapes

without altering the final result, that one blastomere in an

egg which has divided into 8 is still able to reproduce a whole

embryo--question it also), we still fail to conceive any means

by which, for instance, a change in the development of a muscle

or nerve can effect a corresponding change in that part of the

germ which is destined to produce a corresponding part in the

descendant.”

Here it will be observed that belief in the inheritance of structural

effects wrought by use and disuse, is rejected because of inability “to

conceive any means” by which the modifications produced in an organ can

effect a correlated modification in the germ of a descendant: failure

to conceive is the test. The implication is that some alternative

hypothesis is accepted because the correlating of a variation in an

organ with a corresponding germ-variation is effected by a means which

_is_ conceivable. This is the hypothesis of Weismann. Concerning its

conceivability I have, in the chapter just named, already written as

follows:--

“If we follow Prof. Weismann we are led into an astounding

supposition. He admits that every variable part must have a

special determinant, and that this results in the assumption of

over two hundred thousand for the four wings of a butterfly.

Let us ask what must happen in the case of a peacock’s feather.

On looking at the eye near its end, we see that the minute

processes on the edge of each lateral thread must have been in

some way exactly adjusted, in colour and position, so as to fall

into line with the processes on adjacent threads: otherwise the

symmetrical arrangement of coloured rings would be impossible.

Each of these processes, then, being an independent variable,

must have had its particular determinant. Now there are about

300 threads on the shaft of a large feather, and each of them

bears on the average 1,600 processes, making for the whole

feather 480,000 of these processes. For one feather alone there

must have been 480,000 determinants, and for the whole tail

many millions. And these, along with the determinants for the

detailed parts of all the other feathers, and for the variable

components of all organs forming the body at large, must have

been contained in the microscopic head of a spermatozoon!” [And

each of them must, throughout all the complex developmental

processes, have preserved the ability to find its way to the

exact place where it was wanted!]

If my Cambridge correspondent is able to conceive this process implied

by the hypothesis of Weismann, I can only say that he has an enviable

power of imagination.

* * * * *

But now comes the strange fact that an impossibility of thought implied

by Weismann’s hypothesis does not cause rejection of it, but yet is

urged as a reason for rejecting an alternative hypothesis which does

not imply it. One objector cannot conceive that “a change in the

development of a muscle or nerve can effect a corresponding change in

that part of the germ which is destined to _produce a corresponding

part_ in the descendant”; and another objector says it is “very hard to

believe” that a functionally-changed organ will so affect spermatozoa

and ova that “_one particular part of them_ will be so altered that

the organisms which grow up from them will be able to present the

same modification on the application of a different stimulus.” It is

tacitly assumed by both that, as in the hypothesis of Weismann so in

the counter-hypothesis, a particular part of the germ-plasm gives

origin to a particular part of the developed organism. But nothing of

the kind is implied. The nature of the counter-hypothesis (at any rate

as held by me) is entirely misapprehended. Anyone who turns back to

the chapters in the first volume where the conception of physiological

units (or constitutional units) was set forth, or who re-reads the

foregoing appendix, will see that there is altogether excluded any idea

of correlation between certain parts of the germ and certain parts of

the resulting organism. The units are supposed to be all alike, and

during the progressive embryological changes local groups of them are

supposed to take on different forms and structures under the combined

forces, general and local, brought to bear on them. This conception

is necessitated by all the evidence. The fact disclosed by the

experiments of Driesch, Wilson, and Chabry, that from fractions of an

ovum structures may be obtained like that obtained from the whole ovum,

only smaller, necessitates it. The fact that any sufficiently large

fragment of a polyp or planarian, no matter from what part of the body

taken, will develop into a complete polyp or planarian necessitates

it. The fact that from an undifferentiated portion of a plant, even

so small as a scale, a complete plant may arise necessitates it. And

it is necessitated by the fact that among plants, roots are produced

by imbedded shoots and shoots by roots, as well as by the fact that

low animals, such as hydroids, if deprived of both head and root,

will develop a head from the root part and a root from the head

part, if their respective conditions are inverted. All this evidence

shows conclusively that the component units of each species, whether

existing in the germ or in the developed organism, are, when not yet

differentiated by local conditions, all alike, and that the notion of

special parts of the germ-plasm correlated with special parts of the

resulting organism, is entirely alien to the hypothesis.

“But how do the units of a modified organ affect the units of the

germ in such wise that these produce an inherited modification of

the organ?” will be asked. This difficulty has been dealt with in

§§ 97_d_, 97_e_, where the analogy between the social organism and

the individual organism has been brought in aid: serving, if not to

furnish a conception, yet to furnish an adumbration. Regarding citizens

as the units of an unfolding society, say a colony, it was pointed

out that the nature they inherit from a mother-society gives them a

proclivity towards a society of like structure, the traits of which

are progressively assumed as the colony grows sufficiently large to

make them possible. At the same time it was pointed out that while the

influence of the entire aggregate on the individuals is seen in this

forming of them into a society of the inherited type, the influences of

local circumstances, and of individuals on one another, in each group,

make them differentiate into appropriate social structures, taking on

fit occupations and industries: the implication being that in virtue

of their inherited natures they all have partial capacities for the

various activities they undertake; so that an immigrant clerk sets up

a tavern, a compositor takes to carpentering, and a university man

rides after cattle or is employed on a sheep farm. Evidence was given

in that place, as in the above paragraph, that the constitutional units

of an organism similarly have all of them potentialities for taking

on this or that structure and mode of action which local conditions

determine. It was further argued that as citizens are continually

being remoulded by their society into congruity with it, and, if

circumstances change them, tend to remould their society; so in the

individual organism, there is this reciprocal action of the whole on

the units and of the units on the whole. Hence it was inferred that the

modified units in any modified part tend to diffuse modifications like

their own through the units at large: being aided by the circulation of

protoplasm, as suggested in §§ 54_d_ and 97_f_. And it was urged that,

however inconceivably complex such a process may be, yet it seems not

incredible when we recognise the probability that an organism is more

or less permeable to undulations propagated by its molecules: Rontgen

rays giving warrant. If such units throughout the tissues may take in

and send out ethereal waves which bring it into rhythmical relations

with others of its kind and tend to produce congruity, it becomes,

if not conceivable still supposable, that throughout the circulating

protoplasm there goes on a continual harmonization of its components--a

moulding of each by all and of all by each. Should it be said that such

a process is too marvellous to be reasonably assumed, the reply is that

it is not more marvellous than heredity itself, which, were it not

familiar to us, would be thought incredible.

* * * * *

But as I have said in the place referred to--“At last then we are

obliged to admit that the actual organizing process transcends

conception. It is not enough to say that we cannot know it; we must say

that we cannot even conceive it:” can only conceive the possibility of

a suggested interpretation.

Hence we have to rely upon evidences of other kinds. Among these, some

which I think dispose absolutely of the fashionable hypothesis while

they harmonize with the opposed hypothesis, have now to be named. That

their implication should not have been generally recognized would have

seemed to me incomprehensible were it not that I have myself only now

observed this implication. The facts are these:--

“Verlot mentions a gardener who could distinguish 150 kinds

of camellia, when not in flower; and it has been positively

asserted that the famous old Dutch florist Voorhelm, who

kept above 1,200 varieties of the hyacinth, was hardly ever

deceived in knowing each variety by the bulb alone. Hence we

must conclude that the bulbs of the hyacinth and the branches

and leaves of the camellia, though appearing to an unpractised

eye absolutely undistinguishable, yet really differ.” (Darwin,

_Variation of Animals and Plants, &c._, vol. ii, p. 251.)

More recently testimony to like effect has been given by Dr. Maxwell

Masters, and has already been quoted by me in a note to § 286 in

illustration of another truth. He says concerning such variations:--

“To the untrained eye, the primordial differences noted are

often very slight; even the botanist, unless his attention

be specially directed to the matter, fails to see minute

differences which are perceptible enough to the raiser or his

workmen.... These apparently trifling morphological differences

are often associated with physiological variations which render

some varieties, say of wheat, much better enabled to resist

mildew and disease generally than others. Some, again, prove to

be better adapted for certain soils or for some climates than

others; some are less liable to injury from predatory birds than

others, and so on.”

In his _Vegetable Teratology_, p. 493, Dr. Masters names another

fact having a like implication--the fact that among seedling stocks

which have not yet flowered, those which will produce double flowers

are distinguishable. He says:--

“This separation of the single from the double-flowered plants,

M. Chatié tells us is not so difficult as might be supposed. The

single stocks, he explains, have deep green leaves (glabrous in

certain species), rounded at the top, the heart being in the

form of a shuttlecock, and the plant stout and thick-set in its

general aspect, while the plants yielding double flowers have

very long leaves of a light green colour, hairy and curled at

the edges, the heart consisting of whitish leaves, curved so

that they enclose it completely.”

What is the general truth implied? Clearly that there exists no such

thing as an independent local variation. Some marked change in the form

or colour of a flower or a fruit draws attention; and, being a change

which interests the florist or gardener, pecuniarily or otherwise,

not only draws attention but usually monopolizes attention: the

natural impression produced being that this variation stands there by

itself--is without relation to variations elsewhere. But now it turns

out that there are concomitant variations all over the plant. Even in

underground bulbs certain appreciable differences go along with certain

conspicuous differences in the flowers. And if along with a striking

change in a flower which the florist contemplates, there go changes

all over the plant not obvious to careless observers but visible to

him, we must infer that there are everywhere minute differences which

even the florist cannot perceive: the whole constitution of the plant

has diverged in some measure from the constitutions of kindred plants.

Every local variation implies a change pervading the entire organism,

manifested in concomitant variations everywhere else.

If so, what becomes of the hypothesis of determinants--the hypothesis

that there is a special element in the germ-plasm which results in a

special local modification in the adult organism? That there are no

facts supporting it has been all along manifest; but now it is manifest

that the facts directly contradict it.

At the same time it may be remarked that while the facts are wholly

incongruous with the hypothesis of determinants and its accompanying

elaborate speculation, they are not incongruous with the alternative

hypothesis. Impossible though it may be to imagine the natures of

those ultimate units peculiar to each species, which have proclivities

towards the particular form of organization characterizing it, yet

that a change of structure arising in one part of the organism is

accompanied by multitudinous changes of structure in other parts of

the organism, is not only congruous with the belief that there exist

such constitutional units, but yields it distinct support. For if, as

above argued, a conspicuous local variation is not the result of any

modification of units special to the locality, but is the result of

a modification of the units at large, then it must happen that such

modification must have its effects on all other parts of the organism;

so that there cannot fail to result all those small concomitant

variations above indicated.

May we not also say that it becomes less incomprehensible that

structural changes caused by use and disuse are inherited? If, as

we see, a local variation spontaneously arising is accompanied by

multitudinous other local variations, implying a necessary correlation

between each local variation and the general constitution of the

organism; then it may be argued that if a marked change of function in

an organ causes increase or decrease of it, this general correlation

implies that there must be a reciprocal reaction between the part and

the whole, tending to re-establish their congruity. The constitution

at large will in so far be changed, and along with its change will go

corresponding changes in the sperm-cells and germ-cells.

* * * * *

Finally let me add, not another argument, but another fact of

observation, of the kind which opponents demand, but which, when they

are from time to time furnished, are severally pooh-poohed as not

enough. Each of them is spoken of as a solitary fact and slighted as

inadequate; and when by and by another is named, this is treated in

the same way; so that the facts which if brought together would be

recognized as sufficient are never brought together. That to which I

refer is set forth in a pamphlet by M. Leo Errera, Professor at the

University of Brussels, entitled “Hérédite d’un Caractère acquis chez

un Champignon pluricellulaire;” being an account of experiments of

Dr. Hunger, at the Botanical Institute in Brussels. First enumerating

various instances of adaptations to climate, as those of plants which,

fitted to northern regions, preserve their constitutional rapidity

of growth and seeding when brought south, and do this for several

generations, he goes on to detail the culture-experiments of M. Hunger,

and sums up the results of these in the following words:--

“On déduit de là que:

“1^o Les conidies d’_Aspergillus niger_ sont adaptées à la

concentration du milieu où a vécu l’individu qui les porte; cet

effet est encore plus marqué après deux générations passées dans

un milieu donné (Expér. I et II);

“2^o II s’agit d’une véritable adaptation et non pas simplement

d’un accroissement de vigueur chez les conidies provenant des

liquides concentrés, car ces mêmes conidies germent moins

rapidement et donnent des plantes moins vigoureuses que

les conidies normales lorsqu’on les sème de nouveau sur le

milieu-type: en s’adaptant aux liquides concentrés, elles se

sont _désadaptées_ du liquide normal (Expér. III);

“3^o Une génération passée sur le liquide normal n’efface pas

l’influence d’une ou de deux générations antérieures passées sur

une liquide plus concentré (Expér. IV).

“Tous ces résultats concordent: _ils montrent une légère, mais

incontestable transmission héréditaire de l’adaptation au

milieu_.”

SUBJECT-INDEX.

(For this Index as it appeared in previous editions the

Author is indebted to F. HOWARD COLLINS, Esq., of Edgbaston,

Birmingham. It has now been adjusted to suit the present revised

and enlarged edition.)

Acacia, foliar organs, =II=, 41, 264.

_Acalephæ_: environment, =I=, 105;

water in, =I=, 173.

_Acari_: special creation and effects of, =I=, 428;

direct transformations, =I=, 706;

segmentation, =II=, 111.

_Acorus calamus_, agamic propagation, =I=, 642.

Acquired characters, inheritance of: functionally-produced

modifications in plants and animals, =I=, 307–13, 318, 526,

541, 562, 692–5; =II=, 618–22;

conceivability of, on the hypothesis of physiological units, =I=,

368–71, 695; =II=, 618–22;

diminution of jaw, =I=, 541–2, 693;

current views on, =I=, 559–60;

cessation of selection, =I=, 560–3;

Eimer’s theory of orthogenesis, =I=, 560;

species differentiation, =I=, 573;

location of mammalian testes, =I=, 573;

tactual perceptiveness, =I=, 602–8, 633, 665, 666, 672–3, 692;

blindness of cave-animals, =I=, 612–3, 647–9;

co-adaptation of co-operative parts, =I=, 621, 663–5;

transmission of disease, =I=, 622–3;

hypothesis supported by telegony, =I=, 624–8, 644–6, 649–50;

views of Darwin and neo-Darwinists, =I=, 630, 685, 690;

why facts in support are meagre, =I=, 632;

degradation of little toe, =I=, 652–3, 673;

neuter forms of social insects, =I=, 658–9, 663–4, 670, 675;

degenerated instinct in ants, =I=, 660–2;

rudimentary limbs of whale, =I=, 669, 692;

importance of question, =I=, 672, 690;

monstrous development of honey-ants, =I=, 683–4;

osteology of Punjabis, =I=, 689;

summary of evidences in support, =I=, 692–5;

genesis of vertebrate skull, =II=, 227;

false joints, =II=, 371, 372;

conceivability of rival hypotheses, =II=, 618–22;

adaptation to environment in _Aspergillus_, =II=, 623.

Acrogens, the term, =II=, 55–6.

(See _Archegoniateæ_.)

_Actinophrys_: a primary aggregate, =II=, 76;

genesis, =II=, 452.

_Actinozoa_: multiaxial development, =I=, 166;

waste and repair, =I=, 213, 219;

differentiation, =I=, 391;

parasitism, =I=, 397;

integration, =II=, 92;

symmetry, =II=, 189, 192;

growth and genesis, =II=, 444.

Activity: the principle of, the essential element in Life, =I=,

113, 114, 122;

not inherent in living matter, =I=, 120;

nutrition and genesis, _résumé_, =II=, 497–9;

and evolution, =II=, 501–4.

Adaptation: general truths, =I=, 227–33, 233–5;

botanical, =I=, 227;

physiological, =I=, 228–33;

psychological, =I=, 229, 230–3;

structural, functional, and interdependence, =I=, 235–9, 240–1,

318;

social and organic stability, =I=, 240–2;

_résumé_, =I=, 242–3;

to varied media, =I=, 479–81, 489, 556;

multiplication of effects, =I=, 512–3, 550;

direct equilibration, =I=, 522–3;

natural selection and equilibration, =I=, 530–5;

non-adaptive specific characters, =I=, 565;

time required for effecting, =I=, 565–6;

an obstacle to re-adaptation, =II=, 11;

of skin and skeleton, =II=, 215, 217;

outer tissue, =II=, 312–4, 387;

skin and mucous membrane differentiation, =II=, 321–2, 389;

vascular system, =II=, 343–4;

osseous, =II=, 352;

muscular, =II=, 368–9, 391;

persistence of force and physiological, =II=, 394;

of reproductive activity to conditions, =II=, 411–6;

vertebræ development, =II=, 563–6.

(_See also_ Co-adaptation.)

Africa, effect of climate on inhabitants, =I=, 30.

Agamogenesis: alternation with gamogenesis, =I=, 266–7, 272–3,

284–94, 336, 592; =II=, 415;

parallelism in karyokinesis, =I=, 267–8;

a process of disintegration, =I=, 276–7;

conditions determining its continuance, =I=, 284–94, 295–7, 330;

physiological units, =I=, 351; =II=, 613;

spontaneous fission, =I=, 582, 584–7, 589–92, 595–6, 599;

remarkable extent of, under favourable conditions, =I=, 591–2,

640–1;

in _Actinozoa_, =II=, 92;

in _Hydrozoa_, =II=, 102;

in _Annelida_, =II=, 103;

innutrition, =II=, 179–80.

_Agaricinæ_, =II=, 139, 257.

Agassiz, L. J. R., zoological classification, =I=, 380.

Aggregates, Animal and Plant (_see_ Morphology).

Agility, a vital attribute, =I=, 578.

Agrimony, floral symmetry, =II=, 42, 167, 170.

Air, in vegetal tissues, =II=, 567–8, 583, 591, 593.

“Air plants,” =I=, 208.

Albumen: properties, =I=, 12;

Lieberkühn’s formula, =I=, 13;

diffusibility, =I=, 19;

in organic tissues, =I=, 41.

Alcohols, properties, =I=, 10–12.

_Algæ_: reproduction, and the dynamic element in life, =I=, 118–9;

multicentral development, =I=, 163, 164;

axial development, =I=, 165;

locomotive powers of minute forms, =I=, 196;

uniform tissue and function, =I=, 200, 586;

gamogenesis, =I=, 271, 279, 280, 283; =II=, 448, 449, 450;

fertility, =I=, 582; =II=, 440, 441;

fission, =I=, 584, 585;

unicellular forms, =II=, 22;

integration in _Confervoideæ_ and _Conjugateæ_, =II=, 25;

pseudo-foliar and axial development, =II=, 28–33, 57;

foliar development, =II=, 76, 91;

branch symmetry, =II=, 145;

cell metamorphoses, =II=, 176;

tissue differentiation, =II=, 244, 246, 251, 252, 256, 272,

385–6;

adaptation of reproductive activity to conditions, =II=, 289;

integration, =II=, 292;

indefiniteness, =II=, 295;

genesis and development, =II=, 463.

Alimentary canal: metabolic processes and agents, =I=, 68–9, 74;

structural traits, =I=, 192;

progressive development, =I=, 195;

relation to environment, =I=, 196;

function, =I=, 205;

segmentation in annelids, =II=, 125;

differentiation, =II=, 301, 302, 321–2, 323–5, 389;

specializations in birds, =II=, 325;

in ruminants, =II=, 327–9;

differentiation of liver, =II=, 329–33;

muscularity, =II=, 364.

Allotropism: of organic constituents, =I=, 4, 9;

muscular action, =I=, 59.

Alloys, melting point of, =I=, 339.

Alternation of generations, misleading application of term, =II=,

84.

(_See_ Agamogenesis _and_ Gamogenesis.)

Amitosis, occurrence of, in morbid tissues, =I=, 264.

Ammonia: properties, =I=, 7, 9;

nerve stimulation, =I=, 55.

_Amœba_: central development, =I=, 163;

a primary aggregate, =II=, 86;

symmetry of encysted, =II=, 186;

symbiosis, =II=, 400.

_Amphibia_: classification of, =I=, 392;

embryonic respiratory system, =I=, 457;

structure and media, =I=, 483;

limb locomotion, =II=, 15;

segmentation, =II=, 122, 225;

outer tissues, =II=, 311;

respiration, =II=, 334, 338;

Owen on skeleton, =II=, 552, 557, 558.

_Amphioxus_: separation of segmentation spheres of egg, =I=, 691;

embryogeny, =II=, 121;

local segmentation, =II=, 125–7, 605;

genesis of vertebrate axis, =II=, 213–6, 218, 222;

development, =II=, 564.

_Amphipnous cuchia_, vascular air-sacs, =II=, 337.

_Anabas scandens_, the climbing fish, =I=, 480, 483.

_Anacharis_ (see _Eloidea_).

Anæsthetics, diverse effects of, =I=, 55.

_Angræcum_, assimilative function of root, =II=, 255.

“Animal Spirits,” vitalism and, =I=, 115.

Animals: nutrition and molecular re-arrangement, =I=, 36–7;

nitrogenous character, =I=, 39–41;

sensible motion, =I=, 57;

metabolism, =I=, 62–77;

multiplication of energies, =I=, 75;

contrasted traits of plants and, =I=, 196;

what is an individual? =I=, 246–7;

solar influence, =I=, 500, 556;

geologic changes affecting, =I=, 501–4, 549, 550, 556;

interdependence with plants, =I=, 504–6, 514; =II=, 398–401;

complexity of influences affecting, =I=, 506;

geographical isolation and origin of species, =I=, 568–9;

vital attributes, =I=, 577–9;

distribution and antiquity of plant and animal types, =II=, 297;

mutual dependence of organisms at large, =II=, 397–408;

hypothetical plant-animal type, =II=, 397;

progressive increase of size, =II=, 401;

laws of multiplication, =II=, 411–6;

rhythm in numbers, =II=, 419;

law of weights and dimensions, =II=, 434.

Animals, domesticated: variation, =I=, 324, 326, 560, 563, 693;

interbreeding, =I=, 345–7, 354; =II=, 615;

pure and mixed breeds, =I=, 354, 625.

_Annelida_: phosphorescence, =I=, 50;

axial development, =I=, 165, 166;

integration, =I=, 363;

larval forms and phylogeny, =I=, 447; =II=, 115;

segmental fission, =I=, 588–9;

segmentation, =I=, 98–101, 103–4, 602–5; =II=, 107–9, 125–7;

lateral gemmation, =II=, 105;

embryogeny, =II=, 119;

bilateral symmetry, =II=, 197–200;

genesis, =II=, 444, 453.

_Annulosa_: regeneration, =I=, 361–2;

distinctive traits, =I=, 392;

origin of type, =II=, 98–110, 602–6;

unit of composition, =II=, 105;

application of term, =II=, 111;

vertebrate symmetry compared, =II=, 203–6;

segmental differentiation, =II=, 207–9;

unintegrated function in _Planaria_, =II=, 373;

development and genesis, =II=, 464;

nutrition and genesis, =II=, 490.

(See also _Annelida_ and _Arthropoda_.)

Anthropomorphism, former prevalence of, =I=, 419.

Ants: utilization of aphids, =I=, 660–1; =II=, 403, 405;

nest-mates, =II=, 405;

castes in social species, =I=, 658–9, 670, 675;

loss of self-feeding instinct in Amazons, =I=, 660–1, 663–4;

monstrous development of Honey-ants, =I=, 683;

bulk and fecundity, =II=, 492.

(See also _Termites_.)

_Aphis_: individuality, =I=, 249, 250; =II=, 603;

parthenogenesis, =I=, 274–5, 289;

fertility, =I=, 582, 640–1; =II=, 476, 490;

utilized by ants, =I=, 660–1; =II=, 403, 405;

over-multiplication checked by lady-bird, =II=, 406.

Aquatic animals, large size attained by, =I=, 156.

_Arachnida_: avoidance of danger, =I=, 92;

oviparous homogenesis, =I=, 271;

segmentation, =I=, 469; =II=, 113, 114;

integration and homology, =II=, 111, 121;

bilateral symmetry, =II=, 198.

_Arcella_: symmetry, =II=, 186;

outer tissue differentiation, =II=, 309.

_Archegoniateæ_: morphological composition, =II=, 32–5;

growth and development, =II=, 50–6;

tubular structure, =II=, 58, 62;

alternating generation not distinctive, =II=, 84;

asymmetry and environment, =II=, 140;

integration, =II=, 293, 296;

individuation and genesis, =II=, 441, 451, 463.

Archenteron: primitive externality, =II=, 301;

formation of cœlom, =II=, 302.

_Archiannelida_: segmentation, =II=, 125.

_Arenicola marina_: polytrochal larvæ, =II=, 109.

Arm: embryogeny of human, =I=, 169;

vicarious use of, =I=, 209.

Army, morphological analogy, =II=, 6.

Arteries (_see_ Vascular System).

_Arthropoda_: uniaxial development, =I=, 165;

protoplasmic continuity, =I=, 190, 629;

excursiveness, =I=, 481;

limb locomotion, =II=, 15;

integration and homology, =II=, 111–4, 121;

bilateral symmetry, =II=, 197–200;

genesis, =II=, 445, 453.

Ascidians: multiaxial development, =I=, 165, 166;

functional differentiation, =I=, 202;

composite individuality of _Doliolum_, =I=, 247;

self-fertilization, =I=, 342;

integration, =II=, 94, 96, 97;

symmetry, =II=, 194;

origin of vertebrate type, =II=, 194, 598, 605.

_Ascomycetes_, reproduction, =II=, 450.

Assimilation: compared with reasoning, =I=, 81–7;

a trait of vitality, =I=, 577.

_Asteroidea_, radial symmetry, =II=, 196.

Astronomy: growth of celestial bodies, =I=, 135;

Schleiden on individuality, =I=, 245;

evolution, =I=, 432, 435;

classification of stars, =I=, 444;

rhythm of, and organic change, =I=, 499–501, 557;

law of equilibration, =I=, 519–20;

co-operation of structure and function, =II=, 3.

Atavism: occurrence of, =I=, 305–6, 314;

digital variation, =I=, 321–3.

Atoms: use of term, =I=, 6, 31;

ethereal undulations and oscillations, =I=, 31–5.

Australia: settler’s usages, =I=, 364;

ratio of jaw to skull in natives, =I=, 541.

Axillary buds, origin and development, =II=, 65–8.

Axis: “neutral” of mechanics, =II=, 210;

genesis of vertebrate, =II=, 212–6, 224–7.

_Bacteria_: fission, =I=, 270;

non-nucleated, =II=, 20;

rate of increase, =II=, 443.

Baer, K. E. von: embryological formula, =I=, 171, 172, 451, 453,

461, 466;

zoological classification, =I=, 383;

on animal transitions, =I=, 480.

_Balanophoræ_, inner tissue, =II=, 274.

Bark: varied development, =II=, 247–9;

physiological differentiation, =II=, 249–50, 258, 386.

_Basidiomycetes_, reproduction, =II=, 450.

Bat, infertility of, =II=, 473.

Bates, H. W., protective mimicry of butterflies, =I=, 398.

_Batrachia_ (see _Amphibia_).

Bean, vascular system, =II=, 573, 591.

Beaver, tail and co-adapted structures, =I=, 616.

Bees (_see_ Insects).

_Begoniaceæ_: multiplication =I=, 224, 317, 442;

individuality, =I=, 251;

development from scales, =I=, 282;

symmetry, =II=, 159, 166;

development, =II=, 271.

Berkeley, M. J., indefiniteness of mosses and ferns, =II=, 296.

Bile, arrest of excretion, =I=, 209.

Bilirubin and biliverdine, function of, =II=, 330, 333.

Biology: definition and divisions, =I=, 124–5;

organic structural phenomena, =I=, 125–7;

also functional, =I=, 127–9;

actions and reactions of function and structure, =I=, 129–30;

genesis, =I=, 130–1;

limited knowledge of, =I=, 131;

evolution, =I=, 432, 434;

sociological analogies (_see_ Sociology).

Biophors, Weismann’s germ-plasm units (_see_ Weismann).

Birds: flesh-eating and grain-eating contrasted, =I=, 68;

growth and expenditure of force, =I=, 142;

size of egg and adult, =I=, 144;

limitations on flight, =I=, 155;

self-mobility, =I=, 175;

temperature, =I=, 176;

functional and structural differentiation, =I=, 201;

food of starving pigeon, =I=, 215;

viviparousness, =I=, 271;

heredity and pigeon breeding, =I=, 305;

atavism in pigeon, =I=, 314;

osseous variation in pigeon, =I=, 321;

classification, =I=, 392;

migrations and change of habits, =I=, 399, 402, 500;

distribution in time, =I=, 410;

Darwin on petrels, =I=, 455;

rudimentary teeth, =I=, 457;

vertebræ, =I=, 471; =II=, 564;

feather development, =I=, 473;

habits of water ouzel, =I=, 485;

egg shells and direct equilibration, =I=, 526;

bones of waders and direct equilibration, =I=, 527;

fertility and nervous development, =I=, 598;

cellular continuity, =I=, 629;

adaptation of structure to environment, =II=, 12;

sexual selection, =II=, 269;

wing spurs, =II=, 313;

outer tissue differentiation, =II=, 314–5, 387;

alimentary canal development, =II=, 325, 327;

muscular colour and activity, =II=, 365–9;

nutrition, =II=, 433;

cost of genesis, =II=, 436;

growth and genesis, =II=, 454, 458;

heat expenditure and genesis, =II=, 468–9, 474;

activity and genesis, =II=, 470–2, 474;

contrasted mammalian fertility, =II=, 470;

eggs of wild and tame, =II=, 478;

fertility of blackbird and linnet compared, =II=, 503;

Owen on skeleton of, =II=, 559, 560, 561.

Bischoff, embryogeny of human arm, =I=, 169.

Bison, modifications entailed by increased weight of head, =I=,

512.

Blackbird, contrasted with linnet in development, =II=, 503.

Blainville, de, definition of life, =I=, 79, 93.

Blastosphere, independence of cells in Echinoderm larvæ, =I=, 185.

Blastula, definition of life and formation of, =I=, 112.

Blood: similarity of iron peroxide, =I=, 17;

metabolic processes, =I=, 69;

segregation of abnormal constituents, =I=, 180;

protozoon life of corpuscles, =I=, 186–7;

morbid changes, =I=, 221, 701;

assimilative power and organic repair, =I=, 221–2;

respiratory tissue differentiation, =II=, 310–1;

pressure in mammals, =II=, 340.

(_See also_ Vascular System.)

Blow-fly, Weismann on nutrition and genesis in, =I=, 678–9.

Boers, Cape, habits and fertility, =II=, 508.

Boismont, A. B. de, on human fertility, =II=, 511.

Bone: growth and function, =I=, 151;

adaptability, =I=, 230; =II=, 217–8;

function and weight, =I=, 308, 693;

mammalian cervical vertebræ, =I=, 394;

evolution and vertebral column, =I=, 470–1;

partial development, =I=, 473;

size of head as influencing, =I=, 512, 536–9;

direct equilibration and strength, =I=, 527;

natural selection and co-adaptations, =I=, 614–21, 674, 677;

rudimentary limbs of whale, =I=, 668, 685, 692;

inheritance of acquired modifications in Punjabis, =I=, 689;

skull development, =II=, 222;

theory of supernumerary, =II=, 223;

Cope on origin of vertebrate osseous system, =II=, 225–7;

differentiation, =II=, 344–56;

false joints, =II=, 370–2;

Owen’s theory of vertebrate skeleton, =II=, 548–66.

Book-worm, food of, =I=, 77.

Born, G., experiments on frog larvæ, =I=, 365.

Botany, biological classification, =I=, 124, 125.

(_See_ Plants.)

_Bothriocephalus_, development, =II=, 490.

_Botryllidæ_: development, =I=, 166;

independence of components, =I=, 247;

agamogenesis, =I=, 641.

Bower, Prof., on alternation of generations, =II=, 84.

_Brachiopoda_, rude vascular system, =II=, 340.

Bradbury, J. B., on vaso-dilators, =I=, 55.

Brain: natural selection and mental evolution, =I=, 553;

analysis of substance, =I=, 596;

weight in higher animals, =I=, 598–9;

size in civilized and uncivilized, =II=, 530.

Branches (_see_ Morphology).

_Branchiæ_ (_see_ Respiratory System).

Brass, effect of antimony on, =I=, 121.

Bread, diamagnetism, =I=, 370.

Breeding: heredity, =I=, 304–5;

in-and-in, =I=, 344–7, 353; =II=, 615;

pure and mixed, =I=, 354, 625.

Bricks, changed equilibrium shown by, =I=, 38, 42.

Brodie, T. G., cell chemistry, =I=, 260.

Brownell, Miss J. L., on birth-rate in United States, =II=, 520.

Brown-Séquard, on inherited epilepsy, =I=, 312, 624.

_Bryophyllum_, peculiar proliferation, =II=, 295.

_Bryophyta_, large size attained by some, =I=, 138.

_Bryozoa_, gemmation, =I=, 588.

Budding (_see_ Gemmation).

Buds: development, =I=, 167–8;

theories of heredity and cauline, =I=, 358–9, 360;

axillary, =II=, 65–9;

effects of nutrition, =II=, 73–4.

Butterfly: protective mimicry, =I=, 398;

instance of tame, =I=, 684.

Cabbage, varieties of, =I=, 302.

_Cactaceæ_: foliar and axial development, =II=, 47–9;

differentiation in, =II=, 258, 276, 282;

vascular system, =II=, 282;

dye permeability and circulation, =II=, 571, 572;

wood formation, =II=, 575, 577, 578, 580.

“Callus,” budding from, =I=, 358, 359.

Camel, natural selection and hump of, =I=, 534.

Canadians, French, fertility of, =II=, 509.

Cancer, the definition of life, =I=, 111;

œsophageal, =II=, 324;

and vascular system, =II=, 343.

Caoutchouc, leaf-structure, =II=, 589.

Capillaries (_see_ Vascular System).

Capillarity, and vegetal vascular system, =II=, 279–80, 286, 568,

570, 585, 587, 592–6.

Carbohydrates: instability, =I=, 10;

the term “hydro-carbon,” _ib._;

molecular changes in, =I=, 42–3;

organic transformation, =I=, 43, 48;

metabolic processes, =I=, 63–77, 262–3; =II=, 362.

Carbon: properties, =I=, 3–5, 20;

compounds, =I=, 6, 7, 9, 10–12, 13, 24–5.

Carbonic acid (carbon dioxide): properties, =I=, 6, 7, 9;

in animal and plant functions, =I=, 62, 214; =II=, 398;

diffusibility, =II=, 331.

Carbonic oxide, properties, =I=, 6.

Carnivores: nitrogenous food, =I=, 47, 68;

katabolic process, =I=, 71;

restricted environment, =I=, 396;

their beneficial effects on animal life, =II=, 405–6.

Carpenter, W. B.: on functional specialization, =I=, 208;

reproduction of seaweed, =I=, 582;

vegetal cell multiplication, =I=, 585;

structure and multiplication of compound organisms, =I=, 586–9;

on fundamental traits of sex, =I=, 595;

nutritive system of invertebrates, =I=, 595;

_Macrocystis_, =II=, 450;

nutrition and reproductive function, =II=, 460.

Cartilage (_see_ Bone).

Castration, effect of, on growth, =II=, 459.

“Castration parasitaire,” Julin on, =II=, 493–6.

Catalysis, and vital metamorphosis, =I=, 39, 43.

Cattell, McKeen, on tactual perceptiveness, =I=, 666.

_Caulerpa_, simulation of higher plant-forms, =II=, 22.

Cave-animals, degeneration of eyes, =I=, 309, 612–3, 614, 647–9,

693.

Cell, the: incomprehensibility of forces at work in, =I=, 118;

protoplasts and their traits, =I=, 181;

the cell-theory, =I=, 184, 252; =II=, 17–21, 85;

differentiation, =I=, 188–9, 194;

the continuity of protoplasm, =I=, 190–2, 194, 628–30; =II=, 21;

its structure, =I=, 253–5;

function of centrosome, =I=, 254–5, 257;

structure and function of nucleus, =I=, 255–6, 258–9;

karyokinesis, =I=, 257–8;

function of chromatin, =I=, 259–65;

fertilization and function of polar bodies, =I=, 266–8;

theories of heredity based on theory, =I=, 356;

Weismann’s differentiation into reproductive and somatic, =I=,

622, 628–30, 633–44;

nucleus absent or dispersed, =II=, 20, 85;

morphological differentiation, =II=, 175–7;

animal morphology, =II=, 228–30;

morphological summary, =II=, 233;

vegetal tissue differentiation, =II=, 249–50, 386;

vascular development, =II=, 279–84, 389.

Centipede, bilateral symmetry, =II=, 198–200.

_Cephalopoda_: bilateral symmetry, =II=, 203;

vascular system, =II=, 341.

_Cercariæ_ (see _Distoma_).

_Cereus_, tissue differentiation, =II=, 276, 283.

Cesalpino, =I=, 377.

_Cestoda_ (see _Entozoa_).

_Chætopoda_, segmentation, =II=, 98, 103, 605.

_Chaja_, wing spurs, =II=, 313.

Change, and definition of life, =I=, 81–90, 113.

Charles, R. H., on inheritance of acquired modifications in

leg-bones of Punjabis, =I=, 689.

Chatié, on single and double stocks, =II=, 622.

Chemistry: properties of organic elements, =I=, 3–5, 20, 22;

of diatomic compounds, =I=, 7–10;

tri-atomic, =I=, 10–12;

poly-atomic, =I=, 12–13, 25;

traits of evolution, =I=, 23–4;

ethereal undulations and atomic oscillation, =I=, 31–6;

chemical affinity and organic change, =I=, 36–7, 38–43;

oxidation and generation of heat, =I=, 46–9, 60;

generation of nerve force, =I=, 52, 60;

metabolism, =I=, 62–77;

physiology and organic, =I=, 127;

flesh constituents, =I=, 154;

composition of organisms and environment, =I=, 173;

organic development and differential assimilation, =I=, 179–80;

chemical units, =I=, 225; =II=, 612;

primitive ideas of elements, =I=, 417;

evolution of organic compounds, =I=, 696–701, 703.

Chestnut, leaf symmetry, =II=, 149, 153.

_Chiton_: simulation of segmentation, =II=, 116, 118;

symmetry, =II=, 202.

Chlorophyll: function, =I=, 65; =II=, 263;

nutrition and absence of, =II=, 74;

constitution, =II=, 262;

symbiotic presence in animals, =II=, 400.

_Chondracanthus gibbosus_, enormous development of reproductive

system, =II=, 487.

_Chordata_, affinities, =I=, 466.

Chromatin (_see_ Cell).

Circle, the, and evolution hypothesis, =I=, 433.

Circulation (_see_ Vascular System).

_Cirrhipedia_: Darwin on retrograde development, =I=, 458;

remarkable transformation in _Sacculina_, =II=, 494–5.

Civilization, human evolution and genesis, =II=, 529–31.

_Cladophora_: integration, =II=, 25;

axial development, =II=, 28.

Classification: subjective conception, =I=, 78;

two purposes of, =I=, 374;

a gradual process, =I=, 375;

botanical, =I=, 377–80, 389–90;

zoological, =I=, 380–9;

incomplete equivalence of groups, =I=, 389, 445–6, 448, 555, 572;

group attributes, =I=, 390–3;

the truths interpreted, =I=, 393–4;

ethnologic and linguistic evolution, =I=, 441–6;

organic evolution, =I=, 443, 447, 555;

differences in kind and degree, =I=, 444–6;

antecedent structural similarity, =I=, 447, 448–9;

Von Baer’s formula, =I=, 451–4, 555;

organic, not uniserial, =II=, 115.

_Classification of the Sciences, The_, and evolution and

dissolution, =II=, 5.

Claus, C, on segmentation in Annelids and Chætopods, =II=, 605.

Clover: flower and axial development, =II=, 45;

symmetry, =II=, 152.

Co-adaptation of co-operative parts: principles underlying, =I=,

234–5, 511–3, 514–5;

slow operation of the process, =I=, 236;

sociological analogy, =I=, 237–40;

reversion under original conditions, =I=, 240;

the analogy continued, _ib._;

the case of bison’s head, =I=, 512;

natural selection an inadequate explanation, =I=, 535, 614–21,

692;

Romanes on “cessation of selection” as effecting, =I=, 560,

561–2;

Weismann’s theories, =I=, 560–3, 663–5, 670, 674–5;

natural selection and economy of growth, =I=, 562;

physiological processes involved, =I=, 566–7;

Wallace’s argument from artificial selection, =I=, 615;

what are co-operative parts? =I=, 616–7;

“intra-selection” examined, =I=, 676–8.

Coal, social effects of supply, =I=, 238–9, 241.

Cocoa-nut, growth and fertility, =II=, 457.

Coccospheres: vital problem presented by protective structures,

=I=, 119;

imbricated plates, =I=, 182.

Cockroach, ousting of European species, =I=, 399.

Cod: ova of, =II=, 435;

growth and fertility, =II=, 454.

_Codium_: symmetry, =II=, 136;

tissue differentiation, =II=, 246.

_Cœlenterata_: rudimentary contractile organs, =I=, 58;

vital changes in polyp, =I=, 95;

axial development, =I=, 165, 166;

environment and structure, =I=, 173;

self-mobility, =I=, 175; =II=, 14, 15;

functional differentiation, =I=, 201, 391;

inactivity and waste, =I=, 213;

reparative power, =I=, 219, 224;

individuality, =I=, 246, 247, 250;

heterogenesis, =I=, 273, 277, 296;

negative disintegration in _Hydrozoa_, =I=, 276, 587;

reproductive tissue, =I=, 281;

differentiation in _Hydrozoa_, =I=, 391;

classificatory value, =I=, 446;

regeneration of fragments, =II=, 90;

integration, =II=, 90, 102, 105, 124;

gemmation, =II=, 91;

tertiary aggregation, =II=, 92, 95, 124;

molluscan affinities, =II=, 115;

radial symmetry, =II=, 188;

symmetry of compound, =II=, 192–3;

segmental differentiation, =II=, 207;

physiological differentiation in _Hydra_ and analogy, =II=, 300;

ciliation of blastula, =II=, 301;

tissue reduplication, =II=, 301–2, 389;

outer tissue differentiation, =II=, 309;

osmosis in _Hydra_, =II=, 339;

vascular system in _Hydra_, =II=, 340, 376;

functional co-ordination, =II=, 376;

symbiosis, =II=, 400;

asexual genesis, =II=, 443–4;

growth and sexual genesis, =II=, 452;

development and genesis, =II=, 462;

nutrition and genesis, =II=, 476.

Cœlom, origin and function, =II=, 302–3.

Collins, F. Howard, jaws and teeth of savages and civilized, =I=,

541.

Colloids: T. Graham on, =I=, 15–8;

diffusibility, =I=, 18–21;

organic, =I=, 21, 25, 26;

pliability and elasticity, =I=, 27;

capillary affinity, =I=, 28;

isomerism, =I=, 59;

instability, =I=, 350;

molecular mobility and diffusibility, =II=, 331;

instability of, and nerve differentiation, =II=, 356–61;

and muscular tissue, =II=, 361–4.

Colonies, autogenous development and parallel in heredity, =I=,

366–8; =II=, 620.

Colour: sensation of, =I=, 54;

phœnogamic, =II=, 75, 265–6;

light and vegetal, =II=, 261–2;

floral fertilization, =II=, 267–9;

sexual selection, =II=, 269;

activity and muscular, =II=, 365–9;

physiological units and mixture of, in offspring, =II=, 616, 617.

Commensalism, organic Integration as displayed in, =II=, 402–4.

_Compositæ_: floral symmetry, =II=, 173.

Condor, weight of, =I=, 155.

_Confervoideæ_, =I=, 279, 280; =II=, 25, 28, 449.

(See _Algæ_.)

_Conjugateæ_, =II=, 449.

(See _Algæ_.)

Conjugation, in _Algæ_, =I=, 279;

in _Protozoa_, =I=, 280; =II=, 452;

can fission persist without? =I=, 637;

relation to growth, =II=, 449.

Connective tissue, Hertwig’s classification, =I=, 189.

Constitutional units, =I=, 369.

(_See_ Physiological Units.)

Consumption, hereditary transmission, =I=, 307.

Co-ordination of actions (_see_ Life).

Cope, E. D., on origin of vertebrate structure, =II=, 225–7.

_Cormophyta_: slight internal differentiation, =II=, 273;

vascular system, =II=, 280.

_Corpuscula tactus_, their function, =I=, 75.

Correspondence, use of word, =I=, 97.

(_See_ Life.)

Cousin-marriages, =I=, 345; =II=, 615.

Cow: what prompts her to mumble a bone? =I=, 120.

Cow-parsnip (see _Heracleum_).

Crab (see _Crustacea_).

Creation (_see_ Special creation).

_Crinoidea_, symmetry, =II=, 195–6.

Crocodile, continuous growth, =I=, 154, 292.

Crookes, Sir W., hypothetical chemical unit “protyle,” =I=, 22, 23.

_Cruciferæ_, floral symmetry, =II=, 164, 171.

_Crustacea_: locomotion of lobster, =I=, 175;

regeneration of limbs, =I=, 224, 360, 589; =II=, 76;

homogenesis, =I=, 271;

genesis and nutrition in _Daphnidæ_, =I=, 290–1;

growth and genesis, =I=, 292;

degeneration of eye in cave-inhabiting, =I=, 309, 614, 648;

hermit-crab parasite, =I=, 397;

changes of media, =I=, 401, 481–2;

retrograde development in cirripedes, =I=, 458;

segmentation, =I=, 468–9; =II=, 114;

Darwin on jaws and legs, =I=, 471;

survival of cirripedes, =I=, 517;

integration and homology, =II=, 111–4, 121, 603;

bilateral symmetry, =II=, 198–201;

eyes, =II=, 318;

dermal structure of hermit-crab, =II=, 322, 387;

fertility, =II=, 453;

nutrition and genesis in parasitic species, =II=, 487;

“castration parasitaire,” =II=, 493–6.

Crystalloids: Prof. Graham on, =I=, 15–8;

diffusibility, =I=, 18–21;

organic, =I=, 21–2, 26.

Crystals: simulation of life in “storm glass,” =I=, 96;

growth, =I=, 135–7, 577;

segregation, =I=, 179, 221, 223;

equilibration, =I=, 337;

physiological units and polarity, =I=, 701–6;

time and formation, =II=, 77.

_Ctenodrilus_, segmental individuality, =II=, 103, 603, 604.

Cube, bilateral symmetry, =II=, 132.

Cunningham, J. T., =I=, vi; =II=, vi;

on non-adaptive specific characters, =I=, 565;

food of blow-fly larvæ, =I=, 678;

arthropod segmentation, =II=, 114;

egg-production of Conger, =II=, 425.

Cuttle-fish, Individuality of _Hectocotylus_, =I=, 250.

Cuvier, zoological classification, =I=, 381.

Cyanogen, properties, =I=, 7, 9.

_Cyclichthys_, dermal structure, =II=, 306.

Dalyell, Sir J., regeneration in _Dasychone_, =I=, 361;

propagation of _Hydra_, =II=, 476.

_Daphnidæ_, heterogenesis and nutrition, =I=, 290–1.

Darwin, C: _Origin of Species_, =I=, 129; =II=, 528;

natural selection and function, =I=, 308–9, 693;

atavism, =I=, 314;

osseous variations in pigeons, =I=, 321;

plant variation and domestication, =I=, 325;

“spontaneous variation,” =I=, 328, 697;

floral fertilization, =I=, 340; =II=, 168, 267, 407, 608;

intercrossing and self-fertilization, =I=, 344, 345;

intercrossing =I=, 347, 611, 669;

his theory of pangenesis examined, =I=, 356–62, 370, 372;

plant-fertilization and distribution, =I=, 397;

habits of birds, =I=, 400;

distribution and natural barriers, =I=, 402, 476;

disappearance and non-reappearance of species, =I=, 406;

distribution in time and space, =I=, 410;

linguistic classification, =I=, 442;

classification of organisms, =I=, 443;

classification and descent, =I=, 448;

on petrels, =I=, 455;

suppression of organs, =I=, 457;

development of _Cirrhipedia_, =I=, 438;

jaws and legs of _Crustacea_, =I=, 471;

aborted organs, =I=, 474, 563;

relations of species in Galapagos archipelago, =I=, 478;

opinions of E. Darwin and Lamarck, =I=, 491;

the term “survival of the fittest,” =I=, 530;

Indirect equilibration by natural selection, =I=, 530–5;

inheritance of acquired characters, =I=, 535–42, 560, 630, 685,

690;

Wallace on natural selection in man, =I=, 553;

misleading connotations of term “natural selection,” =I=, 609,

695;

caste gradations and jaws of driver ants, =I=, 658;

attachment of climbing plants, =II=, 276–7;

vegetal fructification, =II=, 294;

earth-worm, =II=, 402;

animal sterility and domestication, =II=, 480, 483;

variation in hyacinth and camellia, =II=, 621.

Darwin, Dr. E., modifiability of organisms, =I=, 490, 492–7.

Death: an arrest of vital correspondence, =I=, 102;

only limit to vegetal growth, =I=, 153;

cessation of co-ordination of actions, =I=, 578, 579;

Weismann’s hypothesis, =I=, 636–8;

physiological integration, =II=, 374, 392;

cause of natural, =II=, 413;

relation to births, =II=, 417.

Definiteness: of vital change, =I=, 87–90, 106, 109;

developmental, =I=, 178;

functional, =I=, 212;

segregation of evolution, =I=, 514–6.

Definition, difficulties of, =I=, 78; =II=, 17.

Degeneracy, morphological obscurations due to, =II=, 12, 13.

_Dendrobium_ (_see_ Orchids).

_Desmidiaceæ_: unicellular, =II=, 21;

linear and central aggregation, =II=, 23;

natural selection and symmetry, =II=, 134, 133;

morphological differentiation, =II=, 177;

tissue, =II=, 244;

genesis, =II=, 440, 449.

Determinants, Weismann’s germ-plasm units (_see_ Germ-plasm).

Development: an increase of structure, =I=, 162; =II=, 461;

primarily central, =I=, 162, 166;

uni- and multicentral, =I=, 163–4, 166–7;

axial, =I=, 164, 167;

uni- and multiaxial, =I=, 165–6;

a change to coherent definite heterogeneity, =I=, 167–70, 179;

Von Baer’s formula, =I=, 171–2;

individual differentiation from environment, =I=, 172–8;

cell-formation, =I=, 225;

discontinuous, and agamogenesis, =I=, 275;

Prof. Huxley’s classification, =I=, 276;

sociological parallel to autogenous, =I=, 364–8; =II=, 620;

retrograde, =I=, 457–8;

inequalities among co-operative parts, =I=, 617;

“heterochrony,” =I=, 655;

continuous and discontinuous vegetal, =II=, 52;

summary of physiological, =II=, 384–90;

nutrition and genesis, _résumé_, =II=, 497–9;

evolution, =II=, 501–5;

commencement of genesis, =II=, 506;

of vertebrate limbs, =II=, 553.

(_See also_ Multiplication.)

_Development Hypothesis, The_, =I=, 417.

Dialects (_see_ Language).

Dialysis, and diffusibillty. =I=, 19, 20.

Diastase, decomposition of, =I=, 38, 40.

_Diatomaceæ_: tissue, =II=, 244;

genesis, =II=, 440, 448.

Diatomic compounds (_see_ Chemistry).

Dicotyledons: growth, =I=, 139, 143; =II=, 63–4, 69–72, 78, 82–3;

uniaxial development, =I=, 165;

stem and leaf functions, =II=, 257;

mechanical stress and wood formation, =II=, 277;

growth and genesis, =II=, 451.

Differentiation (_see_ Morphology _and_ Physiology).

_Difflugia_: primary aggregate, =II=, 86–7;

symmetry, =II=, 186;

outer tissue differentiation, =II=, 309.

Diffusion, of colloids and crystalloids, =I=, 18–20; =II=, 331.

Digestion: action of nitrogenous compounds, =I=, 69;

obesity, =II=, 480–4;

fertility, =II=, 514.

Dimorphism: floral, =I=, 534;

sexual, in parasites, =I=, 315;

social insects (_see_ Insects).

Dinosaurs, size of, =I=, 139.

_Diphyes_: individuality, =I=, 246;

symmetry, =II=, 192.

Disease: segregation of blood constituents, =I=, 179;

changes in blood from, =I=, 221, 701;

heredity, =I=, 306–7, 312–3, 622–3;

belief in supernatural origin, =I=, 419;

parasitism and special creation, =I=, 427;

morbid products as specific characters, =I=, 567;

telegony, =I=, 646;

dermal structure, =II=, 306;

intestinal muscular hypertrophy, =II=, 325;

indigestion and alimentary canal development, =II=, 328;

jaundice and bilirubin, =II=, 330;

localization of excretion, =II=, 331;

membranes in inflammatory, =II=, 343;

osseous differentiation in rickets, =II=, 352;

fatty degeneration, =II=, 482.

Disintegration, physiological (_see_ Physiology).

_Distoma_: metagenesis, =I=, 273–4;

disintegration of genesis, =I=, 276;

cycle of generations, =II=, 489.

Distribution: physical limits, =I=, 396;

organic environment, =I=, 396–8;

parasitic conditions, =I=, 397–8;

simultaneity of agencies affecting, =I=, 398;

mutual encroachments of species, =I=, 398–401, 477, 489;

facts disproving pre-adaptation to habitats, =I=, 401–3, 411–2;

of animals and plants in time, =I=, 404–11, 412;

ousting of native species in New Zealand, =I=, 477;

local influences, =I=, 477–9, 489;

through varied media, =I=, 479–85, 489, 556;

past and present organic forms, =I=, 485–9, 556;

complex organization and, =II=, 296–7.

Division of labour, physiological (_see_ Labour).

Dog: contrasted lives of tortoise and, =I=, 103, 104;

inherited habits, =I=, 309, 573;

abnormal digits, =I=, 324;

interbreeding of divergent varieties, =I=, 565;

decrease of jaw, =I=, 615, 693;

telegony, =I=, 645;

conditions affecting fertility, =II=, 474, 479.

Dohrn, theory of vertebrate structure, =II=, 606.

_Doliolum_, combination of individualities, =I=, 247.

Domestication (_see_ Animals).

Doubleday, E., on nutrition of genesis, =II=, 510–2.

Driesch, separation of segmentation spheres of _Echinus_ ovum, =I=,

691; =II=, 618.

Dropsy (_see_ Disease).

_Drosera_: individuality, =I=, 251;

proliferous growth, =II=, 75.

Du Bois-Reymond, E. H., electricity from muscles and nerves, =I=,

50.

Dumas, antithesis of animals and plants, =I=, 62.

Dwarfs, Hindu family of, =I=, 316.

Ear, development of vertebrate, =II=, 318, 320.

Earth, climatic rhythm and organic change, =I=, 499–501, 557.

Earth-worm: bilateral symmetry, =II=, 199, 200;

mould production, =II=, 402.

_Echinococcus_ (see _Entozoa_).

_Echinodermata_: independence of blastosphere cells, =I=, 185;

protoplasmic continuity in embryos, =I=, 190;

separation of segmentation spheres of ovum, =I=, 691; =II=, 618;

symmetry, =II=, 191, 195–6.

Economy: of growth in natural selection, =I=, 536, 562;

a trait of organic evolution, =II=, 501, 504.

Ectoderm: functional differentiation, =I=, 202, 203;

functional vicariousness, =I=, 209;

reproductive function, =I=, 281.

Effects, Multiplication of: variation, =I=, 329–30, 333;

organic evolution, =I=, 511–4, 515, 517, 549, 557; =II=, 405–6;

morphological development, =II=, 7–9, 234;

physiological differentiation, =II=, 390–1, 392.

Eggs (_see_ Embryology).

Eimer, T., theory of orthogenesis, =I=, 563–4.

_Elasmobranchii_: protoplasmic continuity, =I=, 629;

segmentation, =II=, 126.

Electricity: genesis in organic matter, =I=, 50–2, 60;

muscular action, =I=, 59;

incomprehensibility, =I=, 121.

Elephant: fertility, =I=, 583, 599; =II=, 459, 506;

cerebro-spinal system, =I=, 598, 599.

Elk, Irish, horns and correlated parts, =I=, 537, 674.

_Eloidea canadensis_: individuality, =I=, 248;

enormous agamic multiplication, =I=, 642.

Elongation, and locomotion in animals, =II=, 15.

Embryology: as aiding biology, =I=, 125–6;

simulated growth, =I=, 136;

initial and final organic bulks, =I=, 143, 158, 161;

fœtal flesh constituents, =I=, 154;

human arm development, =I=, 169;

Von Baer’s formula, =I=, 170–2, 451–4, 466;

embryonic heat, =I=, 177;

spherical organic form, =I=, 177;

unit-life in multicellular organisms, =I=, 185–6;

functional differentiation, =I=, 203;

individuality, =I=, 246–7;

unspecialized reproductive tissue, =I=, 279–83, 317;

changes following impregnation, =I=, 283–4;

nutrition and vegetal growth, =I=, 285–8, 295–7;

and animal growth, =I=, 289–94, 295–7;

physiological units and heredity, =I=, 317–9;

variation and parental functional condition, =I=, 324;

uterine environment, =I=, 327–8;

physiological units and variation, =I=, 330–4, 458;

fertilized and unfertilized ova, =I=, 340–1;

hermaphrodism, =I=, 341–2, 344;

sociological parallel, =I=, 366–8;

evolution hypothesis, =I=, 434, 436, 453, 454, 555;

petrel development, =I=, 455;

substitution and suppression of organs, =I=, 456–8, 466, 472–3;

structural proclivities of physiological units, =I=, 458;

abridgment of stages, =I=, 458–9, 464;

disappearance of intermediate forms, =I=, 459–60, 463;

pre-adaptation, =I=, 461–3;

discrimination of species in early stages, =I=, 461;

anomalous persistence of ancestral traits, =I=, 463–5;

phylogeny, =I=, 486;

egg-shell function, =I=, 527;

genesis of grades in social insects, =I=, 654–6, 658–9, 679–80;

determination of sex, =I=, 657;

order of development qualified by needs, =I=, 679;

osteology of Punjabis, =I=, 689;

direct transformations and physiological units, =I=, 706;

transformation of blastema, =II=, 20;

arrest of growth and innutrition, =II=, 73;

development of segmented animals, =II=, 100–2, 602;

adaptive vertebrate segmentation, =II=, 118–23, 124, 223–4,

605–6;

animal cell morphology, =II=, 228;

primary differentiations of germinal layers, =II=, 300–2;

lung development, =II=, 333–4;

mammalian ova-maturation, =II=, 342–3;

movements of ova, =II=, 356, 363;

modifications in mole, =II=, 391;

genesis and nutrition, =II=, 424, 425;

fish ova, =II=, 435, 454;

cost of genesis, =II=, 435–6;

number of birds’ eggs, =II=, 454–6, 478;

heat and genesis, =II=, 468, 474;

activity and genesis in birds, =II=, 470–2, 474;

vertebrate limb development, =II=, 553;

ossification in vertebrates, =II=, 556;

Owen’s vertebrate theory, =II=, 563;

development of vertebræ, =II=, 564.

(_See also_ Multiplication.)

Embryology of conceptions, =I=, 451.

Emigrants, type of organization among, =I=, 364; =II=, 620.

Endoderm: functional differentiation, =I=, 202, 203;

functional vicariousness, =I=, 209.