former requires less care. In all parts of the world
172 EXPERIMENTAL EVOLUTION LECT.
some vegetable species are predominantly cultivated :
in India rice, in Europe wheat, in Oceania the taro-
plant, and so on. And while little more than nothing is
done at the present time to increase our animal re-
sources, much is being done every day to cultivate
new plants, for food, pleasure, or drugs. But more
remains also to be performed, and I doubt whether
the hundred or more species which Sir Joseph Hooker
pointed out in his Flora Tasmania as being suitable
for cultivation, have all been added to those which have
been known to mankind since the long-past ages when
agriculture began to be evolved. Four centuries have
now elapsed since the American continents were dis-
covered : how many species have been added to those
which were already under cultivation ? Some forty
species, among which, it is true, we must include the
potato, arrow-root, cinchona, tobacco, tomato, pine-
apple, indian-corn ; but are there not many more
which it would prove beneficial to cultivate ? But
this is the business of the future, and ours is with the
past. 1 Many of our cultivated plants differ but
1 While thus advocating the necessity of turning to a better account
the numerous plants which exist and may be, by cultivation, made very
profitable to man in one way or another, I perceive that Prof. G. L.
Goodale was addressing the American Association for the Advancement
of Science on the same topic at the same time. I will merely refer
the reader to his very interesting paper published in the American
Journal of Science, under the heading : Useful Plants of the Future.
Some of the Possibilities of Economic Botany (pp. 271-303), where
iv WILD AND CULTIVATED TYPES 173
slightly from their wild congeners, especially when
we consider plants which have been cultivated only
within recent times. De Candolle 1 shows that out of
247 cultivated species, 169 have enough resemblance
to some wild species to allow us to trace with exact-
ness their origin in the latter. In five cases there is
room for doubt ; in four, the cultivated species although
unlike the wild one is not different enough to
prevent us from tracing its origin ; in fifteen the
differences are greater, and the question remains open
whether there are here distinct species or mere
varieties ; in twenty-four cases wild forms are met
which may be cultivated plants which have been dis-
persed and have become naturalised ; in three cases
the wild and cultivated forms differ to the extent of
being considered as distinct species ; in three cases
the species are distinct ; in twenty-four the wild form
is unknown, but some may yet be recognised after
more careful investigation. Upon the whole, then,
out of 247 cultivated species of plants 113 exist in the
wild as well as in the cultivated state, identical or more
or less modified ; twenty-seven are doubtful ; and
twenty-seven have not been found growing wild. Such
is the result obtained by De Candolle in his valuable
a large amount of useful information and valuable suggestions are
embodied (April, 1892).
1 Origine dcs Plant es Cultivces, 1883.
174 EXPERIMENTAL EVOLUTION LECT.
investigations. Among these 247 species there are
seven which are rapidly becoming extinct. 1 We thus see
1 The following is De Candolle's list :
I. Species spontaneously growing in the wild state, with all
the appearance of indigenous species, and identical with
the cultivated species 1 69
Of these 169 species 31 are of very remote origin ; 56
have been cultivated for more than 2000 years ; the others
are of unknown date.
II. Species of the same category as I., but which have been
found in a wild condition in one locality only, and only by
one observer 3
Cucurbita maxima. Faba vulgaris. Nicotiana tabacum.^
III. Species seen and noticed, but not gathered, by non-
botanical observers who may have been mistaken (old
authors) 2
Carthamus tinctorius, Triticum milgare,
IV. Species found in a wild state, by botanists, under forms
which differ slightly from those which are cultivated, but
not enough to prevent most botanists from recognising
that both are of the same species 4
Olea europea, Oryza saliva, Solanum tuberosum, Vitis vinifera.
V. Species found in a wild state, but considered by some
authors of different species, by others, of different variety,
when compared to the cultivated forms... 15
Allium ampeloprasum porrum, Cichorium endivia
var.*, Crocus sativus var., Cucumis melo*, Cucurbita
pepo, Helianthus tuberosus, Lactuca scariola sativa,
Linuni usitatissimum anmuim, Lycopersicum esculen-
tum, Papaver somniferum, Pyrus nivalis var., Ribes
Grossularia*, Solanum melongena, Spinacia oleracea var. *,
Triticum monococcum.
1 Italicised names are those of species which have been cultivated for
a very long time ; names with an * are those of plants cultivated
for less than 2000 years.
iv WILD AND CULTIVATED TYPES 175
that the greater number of cultivated plants are known
also in their wild condition. This result may seem
surprising and we may wonder at it. As De Candolle
VI. Species found in a sub-spontaneous condition, similar to
any one of the cultivated forms, but which are perhaps
cultivated species having run wild 24
Agave americana, Amarantus gangeticus, Amygdahis
persica, Areca catechu, Avena orientalis*, Avena sativa,
Cajanus indicus*, Cicer arietinum, Citrus decumana,
Cucurbita moschata, Dioscorea japonica, Ervum ervilia,
Ervuni lens, Fagopyrum emarginatum, Gossypium bar-
badense, Holcus saccharatus, Holcus sorghum, Indigofera
tinctoria, Lepidium sativum, Maranta arundinacea, Nico-
tiana rustica, Panicum miliaceum, Raphanus sativus,
Spergula arvensis.
VII. Species found in a sub-spontaneous condition, but different
enough from the cultivated varieties to allow most botanists
to consider them as distinct species 3
Allium ascalonicum* (form of A. cepal), Allium scoro-
doprasum* (form of A. sativum ?), Secale cereale (form of
some other Secale ?).
VIII. Species not found in a wild condition, nor in a sub-
spontaneous state, having perhaps originated in cultivated
forms, but too widely different not to be commonly called
species 3
Hordeum hexastichum (derived from H. distichum?},
Hordeum vulgare (derived from H. distichon ?), Triticum
spelta (derived from T. vulgare ?).
IX. Species not found in a wild or sub-spontaneous condition,
having originated in countries whose indigenous flora is
not yet sufficiently known, but where wild species exist
which are perhaps the same 6
Arachis hypogaea, Caryophyllus aromaticus, Convol-
vulus batatus, Dolichos lablab*, Manihot utilissima, Pha-
seolus vulgaris.
176 EXPERIMENTAL EVOLUTION LECT.
says, "we should have believed a priori &&&. a much
larger number of species which have been cultivated for
more than 4,000 years, would have departed from the
original type to such a degree that the latter could not
be recognised. It appears, on the contrary, that the
wild forms have generally persisted." And he goes
on to explain this fact in two ways. First of all, the
period of 4,000 years is comparatively short, when we
consider the duration of most phanerogamous species ;
and on the other hand, intercrossing between the
wild and the cultivated forms may have prevented
the production of considerable differences between
them in all cases where the wild form persisted. This
last view is very important and goes far to explain
why the cases where the wild progenitor is not re-
cognisable are not more frequent ; and if it is correct,
we should find the largest departure from the original
X. Species not found in a wild or sub-spcitaneous condition,
having originated in countries whose indigenous flora is
yet incompletely known, but more different from the wild
species of these countries than in the preceding case 18
Amorphophallus konjak, Aracacha esculenta, Brassica
chinensis, Capsicum annuum, Chenopodium quinoa, Citrus
nobilis, Cucurbita ficifolia, Dioscorea alata, Dioscorea
batatas, Dioscorea sativa, Eleusine coracana, Lucuma
mammosa, Nephelium Litchi, Pisum sativum*, Saccharum
orncinarum, Sechium edule, Trichosanthes anguina*, Zea
Total 247
iv VARIETIES DUE TO CULTIVATION 177
type in species cultivated in countries where the wild
form does not exist.
The foregoing facts show that some modification is
due to cultivation, in cultivated plants, since some
species exist which are not recognised in the wild
state, such as indian-corn, sugar-cane, wheat, etc. But
numerous modifications are met with, when we con-
sider our cultivated species themselves, and investigate
the orgin of the varieties they exhibit. Here, culti-
vation shows itself as having played an important
part. Let us consider, for instance, the cabbage,
Brassica oleracea, which is most probably a European
species. While Theophrastus recognised three varie-
ties, Pliny was acquainted with six, Tournefort with
twenty, and De Candolle enumerates more than thirty.
These varieties are probably all due to cultivation, and
in some cases the differences between them are very
considerable, and the differences between the varieties
and the parent form, which still exists in France and
England, are greater still. Almost every part has
varied in this species, from the root to the tip of the
leaves and the peduncles of the flowers. Compare
Brussels sprouts and Hungarian turnips, cauliflowers
and common cabbage, for instance, or let us turn
to the common kidney bean (Phaseolus vulgaris) ;
here also varieties are numerous. The potato has
also a large number of varieties although its cultiva-
N
i;8 EXPERIMENTAL EVOLUTION LECT.
tion is of recent origin ; among the radishes consider-
able differences obtain, whatever their original form
may have been ; and the same is true of carrots, lettuce,
strawberries, peaches, pears, apples, oranges in fact,
of every cultivated species we are acquainted with.
In all these species, and also in all plants which are
cultivated for the sake of their flowers, or because
they provide drugs which are of use to man, in all
vegetable species, in short, which mankind cultivates
for some reason or other, numerous varieties exist,
and in many cases we meet with twenty, thirty, or
forty varieties, if not even more, in the same species.
These varieties man is responsible for : he has made
them, he has evolved them out of the species, and
some are of very recent origin, such as the Brussels
sprouts, for instance some were made yesterday, and
others will appear to-morrow. The process may be
indefinitely varied, and so long as man cultivates
plants he has the right to expect to create new
varieties. The method used in such creations is no-
wise mysterious, and all breeders, horticulturists, and
gardeners are acquainted with its application.
The mere enumeration of our garden vegetables,
fruit trees, commercial and industrial plants, garden
trees and flowers, and even their names show that
variability exists amongst cultivated plants as well
as among the wild species, and in plants generally
iv INFLUENCE OF ENVIRONMENT 179
as well as in animals. It is because plants and
animals vary naturally or spontaneously here spon-
taneously merely means from unknown causes that
man has been able to select among the variations
and to make them become permanent. And when
we see how very different are the lines along which
the same species has varied take the cabbage, for
instance, or the dog we are warranted in drawing the
conclusion that variability is very considerable among
cultivated or domesticated organisms. 1
We must now consider the last of the three groups
of facts which lie at the basis of experimental trans-
formism. We have considered variability in the state
of nature, and shown that it is to be met with in all
parts of the organism ; we have also shown that the
same variability obtains among cultivated plants and
domestic animals whose numerous varieties are the
result of man's selection. We must now refer to the
facts which show how natural variability may be
determined or facilitated. These facts may be
arranged under the general heading of the influence
of environment in the production of variations. 2 Their
1 See De Candolle's Origine des Plantes Cultivees, and Sturtevant's
important series of articles on Originof Cultivated Plants, in American
Naturalist y 1887-89.
- Besides Samper's well-known Animal Life (published in the Inter-
national Science Series], the reader will find a large body of subsequent
literature condensed in J. Arthur Thomson's Synthetic Summary of the
N 2
i8o EXPERIMENTAL EVOLUTION LECT.
interest lies in the fact that they can help to show us
how and how far we can produce variation instead
of having to wait for its spontaneous appearance. It
must be said that up to the present date but little has
been done in this line. Such investigations are only
of speculative interest at least they seem so to most
people and they require much time and patience as
well as favourable conditions which are seldom
offered by our city laboratories. On the other hand,
we are allowed to use many facts of observation in
this demonstration of the influence of environment
upon parts or the whole of living organisms : they are
of as much value as direct experiments when we can
really ascertain what are the influences which have been
in action. Between observation and experimentation
there is not as much difference as is commonly said, and
when the conditions under which any phenomenon is
observed can be exactly recognised, the result of the
observation has all the value of that of an experiment. 1
The investigation of the direct influence of environ-
Influence of the Environment upon the Organism. Proc. Roy. Phys.
Soc. Edin. 1887.
1 An observation made under circumstances which allow all the
elements which co-operate to be well ascertained has as much worth as
an experiment ; the only difference being that in the latter case the
experimenter's will has determined the conditions while in the former he
has had no control upon them. But if he is exactly acquainted with
these, the result is quite as valuable, and the difference lies only in the
mental process which precedes the recording of the result.
iv ENVIRONMENT AND LIFE 181
ment illustrates from the very first a fact which is
more or less familiar to all, the fact that living organisms
can withstand, generally speaking, but a small amount
of environmental modification. They are in so many
ways, and by so many parts, dependent upon the ex-
ternal medium, their adaptation to it is so very close,
and the slightest change in environment is apt to react
on such a large proportion of the vital functions, that
we cannot wonder at the enormous influence which
external modifications can exert on life. Suppose
for instance the very small percentage 0,030-0,034% of
carbonic acid which always exists in our atmosphere,
were to disappear, life would soon be extinct on the
whole earth, because plants cannot do without it, nor
animals without plants. Thus a very small change,
which would be perceived only through the use of precise
methods and instruments, and could not be detected by
our unaided senses, would suffice to ruin all life. This
instance shows how very close is the adaptation
between organisms and their environment, and
teaches the need of care in all our experiments on
the action of the latter on the former. A great
number of instances are known which show the
considerable influence of minute external variations,
but none, I think, is more cogent than that which I
gather from the excellent Etudes chimiques sur la
Vegetation of Jules Raulin (Paris, 1870). This writer,
182 EXPERIMENTAL EVOLUTION LECT.
while investigating the influence of the different
elements which go to make up that complex whole
which we call environment, has studied the influence
of many chemical substances upon the growth of
Aspergillus niger. After having ascertained the
exact nature and proportions of the chemical sub-
stances which are required to provide for the plant
the best suitable medium, he has investigated the
influence of some chemicals which do not contribute
to the making of that medium. Some of them exert
a most unfavourable influence ; thus bichloride of
platinum for instance prevents all vital manifestations
of Aspergillus ; even when added in the very minute
dose of y~oVo-, ** kills the plant. With bichloride of
mercury these results are still more striking, as the
dose of -5 T oVcro i s enough to kill Aspergillus ; and
with nitrate of silver the results are still more
surprising : add only i^nhnnr an d death ensues.
It even happens that when Aspergillus is made to
grow in a silver cup, the plant soon dies, because
some of the silver dissolves in the liquid medium, and
although there is not enough of the metal in the
liquid to allow its detection through chemical
analysis, the plant detects it immediately, and shows
that it feels the influence of the poison. Similar
facts are very abundant now, since bacteriology has
sprung into existence, and we all know of the con-
iv ENVIRONMENT AND LIFE 183
siderable influence exerted on micro-organisms by
very dilute reagents. Very minute doses may kill,
in more or less time, most bacteria, and this pro-
vides a basis for the prevention and treatment of
many diseases due to pathogenetic organisms, and
for the disinfection of places where pathogenetic
organisms are supposed to exist. It is needless
here to quote instances. But this investigation has
led to some interesting results, in showing also that
different organisms require different quantities or
proportions of the same substance to cause death, and
that even the same organisms, under different forms,
require different proportions. Here again, in these
very minute and elementary organisms, we find
physiological variability or variation in play ; here
again, in these minute cells, where function would
at first glance appear very elementary, great differences
exist in reaction towards external agents, and hence
in intimate physiology. We know, for instance, that
while bacteria are killed, in one species, at 80 or 90
centigrade, the spores of the same species require 100
or 120; that one species is killed at 40 or 50,
another at 70, 80, or 100 ; that the one thrives well
in such and such a culture, while the other requires
very different media. Here also, once more, physio-
logical variability is in action ; the bacillus of tuber-
culosis, for instance, thrives in bouillon of herring with
1 84 EXPERIMENTAL EVOLUTION LECT.
glycerine, or of clams, or of monkey, hen, or goose,
while in rat broth it becomes very feeble. Each
micro-organism has its very marked preferences as
regards temperature and chemical conditions, and the
susceptibility to variation in these conditions is so very
marked, that while the fowl is too warm-blooded to
allow anthrax to develop, it is enough to cool the
animal artificially to render it inoculable.
These facts show that the correspondence between
the environment and the organism is very close, and that
very slight alterations are enough to cause death, and
the result is that in the experimental investigation of
the influence of environment upon variability, we
must be careful to handle our methods with great
prudence.
But, on the other hand, while in all cases very
slight modifications in environment are apt to
destroy life especially as concerns chemical environ-
ment we often justly wonder at the extent of the
modifications which may be introduced into the latter
without impairing the vital functions. Micro-organ-
isms afford numerous instances of this fact, but I
prefer giving some examples from the higher organ-
isms. It is a familiar fact that while most aquatic
animals or plants die very quickly when transferred
from sea to fresh water or from fresh to sea water,
a number of them withstand the change perfectly
iv BEUDANT'S EXPERIMENTS 185
well, and many fishes are known to spend part of
their life in each of these media. Direct experi-
ments on this matter were made in the beginning of
the century by Beudant ; and the results were fully
recorded by him in a paper read to the Academy of
Sciences. 1 While sudden passage from one medium
to another was in most cases conducive to death, he
has shown that a gradual passage may be attended
with success. A number of Lymnaea, Planorbis,
Physa, Ancylus, Paludina^ etc. were divided into two
sets ; the one lived in fresh water, the other were put
into fresh water to which, every day, a small quantity of
salt was added. After a few months, when in the
latter case the saltness was 4 / the number of the
foregoing individuals which were yet living in the
salted water was nearly exactly the same as that of
the individuals yet alive in the fresh-water aquarium :
in both aquaria the same number of animals had been
originally introduced, and out of 400 there remained
170 in salt water, 184 in fresh water.
Other species suffered more ; while only 40 /
Paludina died in fresh water, 71*54 % died m sa lt
water, and while Unto and Anodonta all throve well
in fresh water, they all died in salt. It is an
1 F. S. Beudant, Memoir c sur la Possibilite de fairs vivre des Mol-
lusques fluviatihs dans les Eaux salees, et des Mottusques marins dans
les Eaux douces, consideree sous le rapport de la Geologic. Paris, 1816,
Journal de Physique, vol. Ixxxiii. p. 268.
1 86 EXPERIMENTAL EVOLUTION LECT.
interesting fact that some of the animals accustomed
to salt water did very well when suddenly transferred
into fresh water, and also when, a month later, they
were again suddenly replaced in the salt solution,
although, in the latter case, animals of the same
species die immediately when they are placed in salt
water without having been gradually accustomed to it
by small doses of salt.
In another series of experiments Beudant tried to
accustom marine animals to fresh water. These
animals, of the genera Haliotis, Cerithium, Buccinum,
Tellina, Verms, Ostrea, Pecten, Mytilus, when suddenly
immersed in fresh water soon died, although some of
the littoral species certainly seemed to resist longer.
After this experiment Beudant tried to accustom the
same species gradually. He had thirty-eight species
at his disposal, in great numbers, and performed the
experiment as in the converse case, adding fresh water
every day, so that after five months the animals were
living in pure fresh water. Out of thirty-eight species,
twenty withstood the change perfectly well ; 370 out of
610 being alive in fresh water, while in salt water
there were 401 ; while the eighteen others were unable
to exist.
Lastly, in a third series of investigations, Beudant
established the fact that marine molluscs are able to
live in sea water containing 30 / of common salt, a
iv AUTHOR'S EXPERIMENTS 187
much larger proportion than that which is commonly
found in the sea.
These experiments show that animals may be
accustomed to live in media which are very different
from those which they normally inhabit, provided the
change is a gradual one. I performed similar investi-
gations some years ago with different animals, 1 with
the view of ascertaining whether it may not be gene-
rally said that the animals which live close to the sea
shore where the fresh water of river and rain must
certainly somewhat sweeten the sea water, are more
liable than others, inhabiting the sea at greater
distances from the coast, to get accustomed to life in
fresh water. I first compared the resistance to fresh
water of three species of Actinozoa, which were A ctinia
mesembryanthemum, Anthea Cereus, and Sagartia
parasitica, putting them at first into an aquarium
containing six litres of salt water and one and a half
of fresh water. All went well. After a few days I
increased the proportion of fresh water, and no change
was apparent, so that on the seventh day I mixed four
and a half litres of sea water with three of fresh water.
On the ninth day death came, carrying off one Sagar-
tia. A second died on the eleventh day, and on the
thirteenth and fifteenth days the two last of this species
1 Henry de Varigny, Beitrag zum Studium des Einjlusses siissen
Wasscrs auf die Seethiere. Centralblait f. Physiologic, 21 January, 1888.
1 88 EXPERIMENTAL EVOLUTION LECT.
died. The other species were doing quite well ; both
are shore-inhabiting animals, while Sagartia lives
at some depth in the sea.