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BIOLOGICAL LECTURES

DELIVERED AT

THE JVIARINE BIOLOGICAL LABORATORY
OF WOOD'S HOLL

In the Summer Session of 189?

Boston, U.S.A., and London
GINN & COMPANY, PUBLISHERS

1896

Copyright, 1896
By GINN & COMPANY

ALL RIGHTS RESERVED

CONTENTS.

LECTURE PAGB

I. Infection and Intoxication. Simon Flexner . . i

II. Ivinmnity. George M. Sternberg .... ii

III. A Student's Reminiscences of Huxley. Henry

Fairfield Osborn 29

IV. Palcsontology as a Morphological Discipline. W.

B. Scott 43

V. Explanations, or How Phenomena are Interpreted.

A. E. DoLBEAR 63

VI. Known Relations between Mind and Matter. A.

E. DoLBEAR 83

VII. On the Physical Basis of A nimal Phosphorescence.

S. Watase loi

VIII. The Primary Segmentatio7i of the Vertebrate

Head. William A. Locy 119

IX. The Segmentation of the Head. J. S. Kingsley. 137

X. Bibliography : A Study of Resources. Charles

Sedgwick Minot 149

XI. The Transformation! of Sporophyllary to Vegeta-
tive Organs. George F. Atkinson ... 169

95273

Biol. Lect., to face page i.

Fig.

J '• vl

^:i}>-'

Experimental Abscess in the Kidney of the Rabbit.
Staphylococcus pyogenes aureus infection.

Fig. II.

.,^mi^i

yCV

" 1 ,. ""',''. .

mi^'

Pk.

V.3 '^

Experimental focal cell necrosis in the liver of the Guinea pig. Ricin intoxication.

FIRST LECTURE.

INFECTION AND INTOXICATION.

SIMON FLEXNER, M.D.

(Associate Professor of Pathology, Johns Hopkins University.)

The science of biology in its widest sense comprises the
study of life in all its forms and activities, both normal and
abnormal. For this reason I shall not apologize for bringing
before you a subject closely related to pathology, a branch
which is concerned only with the abnormal forms and activities
of life.

The underlying principles, which are to-day the subjects of
thought and research in the branches usually classed as the
biological sciences, are not essentially different from those
which are also found in the field of work which more pecu-
liarly belongs to pathology. Nor is pathology any longer a
study, the subject matter of which is limited to man and the
higher animals. Its application to the lower animals, and
even to plants, has been so successful that we are now
justified in looking to the comparative study of disease pro-
cesses for the solution of some of the many still obscure prob-
lems in human pathology.

Manifestly it would be neither possible nor profitable to
attempt to compass in so brief a time the entire field of path-
ological research. It becomes necessary, therefore, to restrict
our attention to a single one of its problems ; and as there is at
the present time none which is attracting more attention than
that relating to the causation and effects of infectious diseases,
I have chosen for this hour the discussion of one aspect of this
subject. My remarks will be prefaced with a few general
statements concerning the parasitic agents of disease. Some

2 BIOLOGICAL LECTURES.

of these belong to the vegetable, others to the animal king-
dom. They are found in the former, among the fungi and
bacteria, and in the latter, among the protozoa, vermes, and
arthropods. While, however, the term pathogenic micro-organ-
isms is arbitrarily applied to all the vegetable parasites, among
the animal parasites only the protozoa should properly come
under this category.

Infectious diseases, then, are such as are caused by pathogenic
micro-organisms, i.e. by fungi, bacteria, and protozoa. In
speaking of the bacterial origin of diseases many writers apply
the term bacteria to micro-organisms of animal as well as of
vegetable origin ; but it must be remembered that protozoa are
not bacteria, although the term pathogenic micro-organisms
can be properly applied to both. I wish, therefore, to empha-
size the fact, that besides the diseases of bacterial origin, there
are also others which are caused by organisms belonging to
the animal kingdom. Typical examples of this class are found
in the different forms of malarial fever which are caused by
the invasion of the blood and organs by organisms belonging
to the group of protozoa.

It must, however, be admitted that the diseases caused by
vegetable parasites are best understood. This fact is easily
explained by our present successful methods employed for the
propagation of these parasites outside the body, whereas as yet
the pathogenic protozoa have not been obtained in the form of
pure cultures outside the bodies of infected animals. The
growth and multiplication of the pathogenic micro-organisms
are associated in many instances with the production of cer-
tain substances of a toxic nature, these poisons, or toxins as
they are called, playing a great role in the causation of disease.
Certain non-pathogenic or saprophytic micro-organisms in the
course of their growth are also capable of producing poisonous
products. There is, however, this marked difference between
these two classes of agents, namely, that whereas the former
are capable of living and of manufacturing the toxins within
the living body, the latter can subsist only in the presence
of dead material. Examples of poisoning by the products
developed by saprophytic bacteria are found in the accounts,

INFECTION AND INTOXICATION. 3

which we so often read, of epidemics occurring suddenly to
large numbers of persons from the ingestion of partly decom-
posed meat, fish, sausage, milk, etc. Infection is therefore to be
distinguished from intoxication, inasmuch as the first presup-
poses the existence of a living agent which enters the body
and survives there, while the second is to be attributed to the
effects of any toxic agent which may be present in the body in
sufficient amount to produce more or less marked symptoms of
disease. The relation of intoxication to infection cannot be
better expressed than in the following paragraph. " It is im-
possible to draw any sharp dividing line between intoxication
and infection ; but it is believed to conduce to precision and
clearness to regard as agents of infection only such as are
capable of reproduction, that is, such as are living organisms
and not include among these agents chemical poisons whether
produced by bacteria or other vegetable cells or by animal
cells" (Welch).

There is perhaps a tendency at the present time to minimize
the importance of the living agents themselves in the produc-
tion of the phenomena of infectious disease, and to ascribe
these entirely to the action of the toxic agents manufactured
by the micro-organisms. But in view of the fact that in several
typical infectious diseases, among which may be mentioned an-
thrax, asiatic cholera, and typhoid fever, it has been found quite
impossible to separate in an active form the toxic products
from the bacteria which produce them, the latter cannot be
regarded as less essential to the production of the disease than
the former. Indeed there are few diseases at present known
in which all the symptoms can be ascribed to the toxic products
of the micro-organisms alone. To quote another paragraph from
Dr. Welch's writings : " In the case of most infectious dis-
eases we can no more separate the actual presence, multiplica-
tion, and specific vital activities of the bacteria within the body
from the disease than we can substitute any chemical substance
for the actual presence and growth of the yeast fungi in the
production of alcohol from sugar."

Yet the role played by the chemical substances developed
from certain bacteria in the production of the phenomena of

4 BIOLOGICAL LECTURES.

disease is not inconsiderable, and we may safely say that only
with such bacteria as produce toxins of great potency, which
are easily yielded by the cells to the surrounding medium,
would it be possible in a given disease for the toxic chemical
substances by themselves to give rise to the same phenomena
as those which are due to the action of the living bacteria.

The study of the nature and action of these toxins, or, as
they are now generally called toxalbumins, has added not a
few interesting facts to our knowledge of poisons in general ;
but, at the same time, it must be understood that the forms
with which we are dealing have not at this time been isolated
in a state of absolute purity, although they have been obtained
in a condition of great potency. Their exact nature is not as
yet well understood. They are believed by most bacteriolo-
gists and chemists to be of an albuminous nature, many
authorities claiming them as enzymes. They are amorphous
bodies and differ essentially from the crystallizable ptomaines,
with which substances they are sometimes confused. Perhaps
the one best studied, certainly the one possessing the greatest
potency, is the toxalbumin produced by the tetanus bacillus.
In the still impure state in which it has been obtained, its
activity has been found to be simply appalling. A single dose
of 0.000.000.05 grm. suffices to produce death after tetanic
convulsions in a mouse weighing 1 5 grams, and it is estimated
that the fatal dose for an adult human being does not exceed
0.23 mg. You will appreciate this fact better if you remember
that the fatal dose of atropine is 130 mg., and of strychnia
from 30 to 100 mg. It should further be mentioned that this
toxalbumin, unlike many of the others, is capable of giving rise
to the same symptoms as the bacillus which produces it.

Another extremely virulent, although less active, toxalbumin
is that obtained from the cultures of the diphtheria bacillus.
Of this 0.4 mg. suffices to kill eight guinea pigs, each weighing
400 grams.

In contradistinction to the tetanus toxin, that produced by
the diphtheria bacillus jdoes not reproduce the entire series of
phenomena of the disease to which it belongs, since the in-
jection of it does not produce at the point of inoculation an

INFECTION AND INTOXICATION. 5

actual false membrane. An extraordinary feature exhibited
by the diphtheria toxin is seen in the extreme slowness with
which it is sometimes known to act. Whereas the poisonous
chemical agents with which we were previously acquainted
exert their effect quickly, and usually after a short interval,
the diphtheria toxin requires at times weeks and even months
for the production of fatal results in the animal inoculated.
For a time it stood alone in this regard, but I have found
similar delay in the action of another toxalbumin, — ricin, a
substance yielded by the seeds of the ricinus communis (castor
plant).

Recent studies have shown that the toxalbumins are widely
distributed in nature. Thus far they have been found among
the lower and higher vegetable forms, and even in the blood of
various animals, such as the eel, snake, and dog.

When we proceed to study the effects of these pathogenic
agents upon the animal body, we find that the phenomena
which are caused by the toxins can often be distinguished
from those due to the actual presence of the bacteria themselves.

Two main forms of lesions of cells can be distinguished in
infectious diseases. In the one, most or all of the cells are
affected ; the lesion is diffuse, and shows itself by an increase
in the size and granulations of the cells, associated often with
the appearance of globules of fat in those otherwise free from
this substance, or with an increase of it in those already con-
taining it. In this way is brought about the so-called paren-
chymatous degeneration of cells, which in extreme cases may
lead to actual cell death (necrosis). This is the typical lesion
ascribed to the action of chemical substances. It is found in
all infectious diseases and in many forms of intoxication.

More interesting are the so-called focal lesions, of which it
may be said that certain ones are caused by bacteria and
others by toxic substances. As an example of the former, a
small abscess may be taken. The bacteria which are most
commonly associated with this pathological process are cocci,
which grow in grape-like clusters presenting often, when cul-
tivated on artificial media, a golden-yellow color, whence the
name ** Staphylococcus pyogenes aureus." If a section be

6 BIOLOGICAL LECTURES.

made through such an abscess (Fig. i), which is located, as so
commonly happens in experimental cases, in the kidney, the
following arrangement is found. The central dark mass repre-
sents the bacteria which have been transported hither by the
blood current, and which have become lodged in the capillary
vessels of the part. Having found here conditions favorable
to their increase, they have grown from a microscopic speck to
a mass large enough to be seen with the naked eye. As a
result of their presence, the surrounding tissue is destroyed,
the destruction being recognizable in the specimen by the
absence of stainable nuclei in this part. Outside the zone of
dead tissue is another in which the cells as compared with
those of the healthy tissue at a distance are greatly increased
in number. This third zone is the area of leucocytic infiltra-
tion, the infiltrating cells consisting of white blood-corpuscles
which have passed out of the vessels to accumulate at this spot
in answer to what is conceived to be a chemical attraction
(chemotropism) exerted by the bacteria and dead tissue. The
leucocytes penetrate as far as possible into the dead tissue,
and become arrested as soon as the poisonous products of the
bacteria are present in quantities sufficient to insure their
speedy destruction. Later a solvent action is exerted by the
bacteria upon the tissues, causing them to liquefy, and con-
verting the contents into "pus," the removal of which leaves
a cavity behind.^

Certain bacteria are capable of exerting an injurious effect
upon tissues and organs of the animal body at a greater dis-
tance from their place of localization. Thus, although the
diphtheria bacillus often remains localized in the throats of
persons suffering from diphtheria, yet very extensive local
lesions are found in the near and remote lymphatic glands, in
the spleen, liver, heart, nerves, and other organs. These
lesions are attributable to the absorption into the body of the
toxalbumin, elaborated by the bacteria in the throat. It is

1 It is not to be concluded that this is the only kind of lesion produced by
bacteria. It is a common one, and has been selected for that reason, and also
because, as far as known, it is never produced by the action of the toxic products
of bacteria alone.

INFECTION AND INTOXICATION. 7

indeed possible by using the bodies of susceptible guinea pigs
and rabbits to show that identical pathological changes can be
produced by inoculation with the toxalbumin alone. A closer
study of the lesions shows them to be different from those
caused by the pus-producing cocci. Such a lesion in the liver
of the guinea pig, resulting from diphtheria intoxication, is
shown in Fig. 2. Note here that a destruction of cells has
taken place, but that no bacteria are to be seen in the neighbor-
hood of the dead cells. The cells themselves present a different
appearance from those seen in the kidney abscess. Individu-
ally they are better preserved ; their outlines are sharper, and
they are more easily made out than the normal cells. Examined
in the fresh state, in physiological salt solution, they present a
characteristic glassy appearance, whence the term "hyaline,"
which is often applied to them. That they are necrotic is
shown not only by the behavior of their protoplasm in the
presence of staining agents, but also by the absence of normal
nuclei in them. For the most part, the nuclei have entirely
disappeared, but here and there a shrunken one can be seen,
and occasionally small pigmented fragments are still preserved.
The intensity of the process evidently grows less as one pro-
ceeds from the center to the periphery of such a focus, and at
the extreme edge a variable number of leucocytes are encoun-
tered. They are never accumulated in quantities, such as are
seen in abscess formation, and such a lesion shows no tendency
to undergo softening with the production of an abscess or
cavity.^

With respect to the toxalbumins which are derived from the
higher plants (ricin, abrin), I have found that the pathological
lesions which they cause are similar, if not identical, with those
produced by the toxalbumins of bacterial origin.

Besides the toxins of vegetable origin, toxic proteid sub-
stances, some of which are of great potency, are yielded by the
animal kingdom. Among these have already been mentioned

1 When it is considered that these toxins are soluble substances, and pre-
sumably in perfect solution in the body fluids, the explanation of their tendency
to produce focal effects is not at once evident. Several hypotheses have been
advanced to account for this phenomenon. See "The Pathological Changes
Caused by Certain So-called Toxalbumins." Medical News, Phila., Aug. 4, 1894.

8 BIOLOGICAL LECTURES.

the toxic constituents of snake venom and the blood of certain
animals. The poisonous effects of snake venom are familiar
to you ; but it is less generally known that the blood of one
species of animal, freed from its corpuscular elements, may
exhibit poisonous properties when introduced in sufficient
amounts into an animal of a different species. Thus the blood
serum of human beings, and of the dog, is highly poisonous to
the rabbit, and that of the lamb to human beings.

In the course of my studies in this direction, I have been
able to show that the injurious effects which the blood of one
animal produces in another is due to the toxic substances con-
tained in the foreign blood, and not alone to the destruction of
the blood-corpuscles of the host which commonly ensues. This
latter phenomenon is spoken of as the globulicidal in contra-
distinction to the toxicidal effects of the foreign serum, and
when the amount of foreign serum introduced into a susceptible
animal is very large, the destruction of corpuscular elements
may be great enough to cause immediate death. The toxicidal
effect is produced much more slowly. The toxic constituents
of the blood serum obtained either from the dog or from human
beings bring about in the tissues of the rabbit changes similar
to those caused by the vegetable toxalbumins which have been
considered.

Having now seen that these agents of intoxication, whether
derived from animal forms of low or high position, or from
vegetable life high or low in point of organization, possess
certain features in common and produce similar pathological
effects when tested upon susceptible animals, it will be of
interest to extend a little further our inquiry into their
properties.

Among the most interesting of these from a theoretical, and
of the greatest significance from a practical standpoint, are the
effects of small and repeated doses of these substances. The
facts elicited by the study of the effects produced by these
bodies when introduced into certain animals in this way have
an important bearing upon the questions of insusceptibility to
disease in general, and are included in the subject matter of
immunity.

INFECTION AND INTOXICATION. 9

The production of immunity to many bacteria or their pro-
ducts is associated with the formation in the animal thus
protected of certain antidotal substances which appear in the
body fluids. It has been shown that a similar immunity for
ricin and abrin can be induced, and more recently the same
has been proved for snake venom. In these instances the
insusceptibility to the actions of the toxic agents is associated
with the appearance in the blood of the treated animals of
antidotal bodies capable of affording protection from these
toxic proteids. In this connection, I have been able to show
that by the exhibition of repeated small doses, rabbits, other-
wise highly susceptible, can be made quite resistent to the
blood serum of the dog.

The foregoing considerations teach that, in the study of the
causation of disease, a widening knowledge is enabling us to
appreciate how much is due to the actions of the living para-
sitic agents themselves, and how much to toxic substances
derived from these and from other sources. The importance
of agents of intoxication is becoming more and more impressed
upon us; and when we reflect that their distribution is co-
extensive with organized nature itself, and that they are
present in the most vital of our body constituents, we begin to
see, if indeed only faintly, what consequences their presence
may entail.

I would bring these remarks to a close by begging you not
to forget that although much has been written upon the disease-
producing micro-organisms, not a small chapter might be added
upon those which are friendly in their nature. When you
consider that the phenomena of decomposition and putrefaction
are executed through their efforts, that the restoration of the
soil, and the fitting of it for the growth of the higher plants,
is effected by a special group of bacteria, you will appreciate
the fact that life on this globe would be impossible for the
higher living forms could these lowly ones be perchance
exterminated.

Furthermore, there are defences set up everywhere in the
animal body through which the invasion of these noxious para-
sites is resisted. Those parts most exposed to their action

lO BIOLOGICAL LECTURES.

are either covered by a dense and relatively impenetrable mem-
brane, or if protected by a barrier less secure, are bathed with
fluids at once injurious to them, and offering mechanical
obstacles to their settlement. Thus for the exterior of the
body we have as a rampart, the skin, and for each orifice its
mucous surface with its own peculiar secretion. Even should
the parasite be able to pass beyond these outposts, its fate is
still insecure, for the lymphatic tissues stand as a closed gate-
way to oppose its further progress ; and beyond these again
are forces still more impregnable, — the body fluids and cells,
which are capable of destroying large numbers of bacteria,
and probably no inconsiderable quantities also of their toxic
products.

SECOND LECTURE.

IMMUNITY.

BY GEORGE M. STERNBERG, M.D., LL.D.
(Surgeon-General U. S. Army, Washington, D. C.)

The resisting power, natural or acquired, which living
animals possess against invasion by pathogenic micro-organ-
isms is commonly spoken of as ** immunity." But we might
include in our definition of the term, used in the biological
sense which we shall attach to it in the present lecture, the
more general resisting power which living animals possess
against saprophytic bacteria. It is hardly necessary to call
attention to the fact that, under suitable conditions as to tem-
perature and moisture, dead animal tissues undergo putrefac-
tive decomposition, — i.e. are invaded by saprophytic bacteria, —
while healthy, living animals resist such invasion. This more
general immunity appears to be due to causes which are the
same or similar to those which enable insusceptible animals
to resist invasion by pathogenic bacteria. There is also an
immunity, which the Germans designate *^ giftfestigtmg,'' which
is manifested by an increased resisting power to the toxic
action of the chemical products of pathogenic bacteria, and
which may be established by introducing these toxic substances
into susceptible animals quite independently of the micro-
organisms which produce them — inoculations with filtered
or sterilized cultures. This corresponds with the acquired
immunity which has been shown to result from the inoculation
of susceptible animals with non-lethal doses of certain toxic
albuminous substances of animal and vegetable origin, — snake
poison, abrin, ricin, etc.

12 BIOLOGICAL LECTURES.

By ''natural immunity" we mean the insusceptibility which
certain species or certain individuals have against infection by
certain pathogenic bacteria. " Acquired immunity " is the
resisting power which results, in originally susceptible animals,
from a non-fatal attack of an infectious disease, or from pro-
tective inoculations with "attenuated" or filtered cultures of
pathogenic bacteria.

As is well known, certain infectious diseases are peculiar to
man, certain others to one or more species of lower animals,
and others still may be transmitted from man to certain lower
animals, or vice versa. Thus typhoid fever, yellow fever,
cholera, measles, etc., are infectious diseases of man, and
during their epidemic prevalence the lower animals show no
evidence of susceptibility to infection. On the other hand,
Texas fever and infectious pleuropneumonia, which are very
fatal to cattle, hog cholera and swine plague, chicken cholera,
etc., are never communicated to those who care for the infected
animals ; in other words, man has a natural immunity against
these diseases. Again, certain infectious diseases are common
to man and to certain species of the lower animals. Thus,
tuberculosis may be transmitted to monkeys, to cattle, rabbits,
guinea pigs, and fowls ; carnivorous animals in confinement,
also, sometimes succumb to tubercular infection. Anthrax
is fatal to cattle, sheep, and small herbivorous animals, and
may be transmitted to man by inoculation, or by the introduc-
tion of dry spores into the respiratory passages — '* wool-
sorter's disease." Diphtheria may be transmitted to cats and
fowls, and cultures of the diphtheria bacillus are extremely
pathogenic for the guinea pig. Glanders, which is a disease of
the equine genus, may be transmitted to man, to the guinea pig,
and to the field mouse ; but house mice have a natural immunity
against infection by this bacillus. On the other hand, field
mice and guinea pigs are not susceptible to infection by the
Bacillus erysipelatus suis, which is very fatal to house mice,
white mice, rabbits, swine, sparrows, and pigeons. There are
also differences in susceptibility to various infectious diseases
among different races of the same species. Thus the Algerian
sheep has an immunity against anthrax ; Texas cattle, as a

IMMUNITY.

13

rule, do not succumb to Texas fever, which is very fatal to
northern cattle ; yellow fever is much less fatal to the negro
than to the white race ; the negro also resists malarial infection
better than the white. In general, carnivorous animals have
but slight susceptibility to the various forms of infectious
septicaemia which are fatal to the herbivora. The introduction
beneath the skin of a mouse or a rabbit of a little putrefying
flesh infusion frequently gives rise to a fatal septicaemia, due
to the presence of one or more species of bacteria pathogenic
for these animals, but harmless for the carnivora which prey
upon them. Were this otherwise, the carnivora would be
destroyed by wounds inflicted in their fights over animals
which had died of infectious diseases or which were in a state
of putrefaction. It appears probable that the immunity of the
carnivora to the infectious septicaemias referred to has been
acquired in process of time by natural selection — survival of
the fittest.

Besides the race immunity referred to, we have differences
in the degree of susceptibility to various infectious diseases in
individuals of the same race. Some individuals or families
have manifestly a special susceptibility to tubercular infection ;
others are especially subject to contract smallpox, as shown by
the occurrence of two or more attacks in the same individual.
Susceptibility also depends to some extent upon age. The
young are especially susceptible to scarlet fever, whooping
cough, and diphtheria. In the lower animals, we find that an
"attenuated virus" which will not kill an adult of a susceptible
species may prove fatal to a very young animal of the same
species.

Immunity, whether natural or acquired, in many cases has
only a relative value, and may be overcome by an excessive
dose or by unusual virulence of the infectious material. This
is true, for example, of the natural immunity of the Algerian
race of sheep as regards anthrax, of the acquired immunity
resulting from vaccination against smallpox, etc. But it does
not apply in the case of animals which have a complete natural
immunity for infectious diseases peculiar to other species.
Thus man never contracts swine plague or infectious pleuro-

14 BIOLOGICAL LECTURES.

pneumonia under any circumstances, and domestic animals
never contract yellow fever or cholera during the epidemic
prevalence of these diseases.

The relative immunity, natural or acquired, to diseases which
are not strictly limited to a single species, may often be over-
come by various agencies acting upon the individual exposed
to infection. Thus Arloing was able to induce symptomatic
anthrax in animals naturally immune for this disease by mix-
ing with his cultures various chemical substances, such as car-
bolic acid, pyrogallic acid, and especially lactic acid (twenty
per cent). Leo has shown that white mice, which are not
subject to the pathogenic action of the glanders bacillus, may
be rendered susceptible by feeding them for some time upon
phloridzin, which gives rise to an artificial diabetes, and causes
the tissues to become impregnated with sugar. Behring
claims to have demonstrated by experiment that white rats
lose their immunity for anthrax when fed for some time upon
an exclusively vegetable diet, or when phosphate of lime is
added to their food ; and he has suggested that the immunity
of these animals may be due to the highly alkaline reaction of
their blood and tissue juices. Nocard and Roux found by
experiment that an attenuated culture of the anthrax bacillus,
which was not fatal to guinea pigs, killed these animals when
injected into the muscles of the thigh after they had been
bruised by mechanical violence. Abarrin and Roger found
that white rats, which are not susceptible to anthrax, became
infected and frequently died if they were exhausted, previous
to inoculation, by being compelled to turn a revolving wheel
for a considerable time. Pasteur found that fowls, which have
a natural immunity against anthrax, become infected and perish
if they are subjected to artificial refrigeration after inoculation.
This has been confirmed by the more recent experiments of
Wagner (1891). According to Canalis and Morpurgo, pigeons
which are enfeebled by inanition easily contract anthrax as
a result of inoculation. Arloing states that sheep which have
been freely bled contract anthrax more easily than others ; and
Serafini found that when dogs were freely bled, the bacillus of
Friedlander, injected into the trachea or the pleural cavity.

IMMUNITY.

15

entered, and apparently multiplied to some extent in the
blood, whereas without such previous bleeding they were not
to be found in the circulating fluid. Certain anaesthetic
agents have also been shown to produce a similar result.
Platania communicated anthrax to immune animals — dogs,
frogs, pigeons — by bringing them under the influence of
curare, chloral, or alcohol ; and Wagner obtained similar re-
sults in his experiments upon pigeons to which he had admin-
istered chloral. In man, clinical experience shows that those
who are addicted to the excessive use of alcohol are especially
liable to contract certain infectious diseases, — pneumonia,
erysipelas, yellow fever, etc.

The pathogenic potency of known disease germs varies as
widely as does the susceptibility of individuals to their specific
action. In general it may be said that the more recently the
germ comes from a developed case of the disease to which it
gives rise, the more virulent it is, and the longer it has been
cultivated outside of the animal body, the more attenuated is
its pathogenic power. Thus, when the discharges of a typhoid-
fever patient find their way directly to a water-supply of limited
amount, a large proportion of those who drink the water are
likely to be attacked ; but when a considerable interval of time
has elapsed since the contamination occurred, although the
germs may still be present, the liability to attack is much less,
on account of diminished pathogenic virulence.

What has been said thus far indicates that infection depends
{a) upon the susceptibility of the individual (predisposition),
{b) upon the virulence of the infectious agent, and {c) upon
the quantity introduced to a vulnerable point, — e.g. beneath
the skin by inoculation or through an accidental wound in
anthrax and other forms of septicaemia, into the alimentary
canal in typhoid fever and cholera, or into the respiratory pas-
sages in diphtheria, influenza, pneumonia, and pulmonary tuber-
culosis. Still another factor may be called into play. In
addition to the specific cause or germ, and the natural or
acquired (by various depressing agencies referred to) predis-
position, a direct exciting cause may be necessary to establish
a localized infectious process. Thus, catching cold may be the

1 6 BIOLOGICAL LECTURES.

exciting cause which develops an attack of pneumonia or
influenza or tuberculosis in an individual having a predisposi-
tion to these diseases, — the specific cause being present ; or
indigestible food in the primae viae may be the exciting cause
of an attack of cholera ; or the irritation resulting from breath-
ing an atmosphere loaded with dust may give rise to tubercular
infection. Again, bruising of the tissues may give rise to an
abscess or a carbuncle in an individual whosQ vital resisting
power is below par, the specific agents of such local infections
(the pus cocci) being widely distributed and frequently found
on the surface of the body and upon exposed mucous mem-
branes in healthy individuals.

A non-fatal attack of an infectious malady, as a rule, is
followed by a relative immunity of longer or shorter duration.
In smallpox, scarlet fever, measles, yellow fever, typhoid fever,
and certain other diseases of man one attack usually protects
during the life of the individual; but exceptions to this rule are
not rare, especially in the case of smallpox. In pneumonia,
diphtheria, influenza, and cholera second attacks are frequent ;
and while a relative degree of immunity is no doubt acquired
as a result of an attack, this is of brief duration.

The production of immunity by protective inoculations was
for a long time limited to a single disease, — smallpox.
Inoculations with virus, obtained from a pustule on a smallpox
patient, were extensively practised before the discovery of
vaccination by Jenner. These inoculations gave rise to a mild
attack of the disease, followed by immunity, which was appar-
ently as complete as that following a more severe attack con-
tracted in the usual way. This method seems to have been
practised by eastern nations long before it was introduced into
Europe. It was extensively employed in Turkey early in the
eighteenth century, and was introduced into England through
the influence of Lady Mary Wortley Montagu. No doubt the
mortality from smallpox was greatly diminished by these
inoculations ; but they were attended by the disadvantage that
the disease was propagated by them, inasmuch as inoculated
individuals became a source of infection for others. Inocula-
tion was still practised in England for some time after the

IMMUNITY, 1 7

demonstration of the protective value of vaccination, but in
1840 it was prohibited by an act of Parliament.

There is some evidence that vaccination as a protection
against smallpox was practised to a limited extent prior to the
time of Jenner. Thus Von Humboldt has stated that it was
known at an early period to the Mexicans. But its introduc-
tion as a reliable method of protecting against smallpox is due
to the patient researches of the renowned English physician,
whose attention was first attracted to the subject in 1768,
although it was not until 1796 that he made his first vaccina-
tion in the human subject. His first public institution for the
practice of vaccination was established in 1 799, and the follow-
ing year the practice was introduced into France, Germany,
and the United States.

In the infectious disease of cattle known as pleuropneumonia,
protective inoculations were successfully made some time
before the demonstration by Pasteur of the efficacy of such
inoculations in anthrax and chicken cholera (1880). Various
methods have been employed. Thus Willems states that the
natives of the banks of the Zambeze cause animals to swallow
a certain quantity of the liquid from the pleural cavity of an
animal recently dead, and thus give them immunity. The
virus has been injected into the circulation by some experi-
menters, and others have proposed to attenuate it by heat.
But the method which has been most extensively employed is
that discovered by the Dutch settlers at the Cape of Good
Hope (the Boers), and consists in inoculating animals in the
tail with serum from the lungs of an animal recently dead, or
with a virus obtained from the tumefaction produced by such
an inoculation in the tail. This secondary virus was very
extensively used by Lenglen, a veterinarian at Arras, who
communicated his results to the Academy of Science at Paris,
in April, 1863, and Willems says, in his last published commu-
nication, that this is the method which he prefers. It is also
the method most extensively employed in Australia, into which
country infectious pleuropneumonia was introduced in 1858.

Toussaint, a pioneer in researches relating to protective
inoculations, has a short paper in the Comptes-Rendiis of the

1 8 BIOLOGICAL LECTURERS.

French Academy of Sciences of July 12, 1880, entitled
" Immunity from Anthrax (' charbon ') Acquired as a Result
of Protective Inoculations."

In this paper he announces his discovery of the important
fact that the anthrax bacillus does not form spores in the tis-
sues or liquids of the body of an infected animal, but multiplies
alone by binary division, — "sa multiplication se fait toujours
par une division du mycelium."

In the same communication he reports his success in con-
ferring immunity upon five sheep by means of protective
inoculations, and also upon four young dogs. We must, there-
fore, accord him the priority in the publication of experimental
data demonstrating the practicability of accomplishing this
result.

But it is especially to the experimental researches of Pasteur
that we are indebted for the development of practical methods,
which have been extensively employed in protecting cattle,
sheep, and swine from the fatal effects of various infectious
maladies, and man from hydrophobia as the result of the bite
of a rabid animal.

Pasteur's inoculations are made with an "attenuated virus,"
— i.e. with a culture of a pathogenic micro-organism which has
a diminished degree of virulence and which when introduced
into a susceptible animal induces a non-fatal and comparatively
mild attack.

The researches of Pasteur and of his followers in this line of
investigation show that pathogenic virulence may be attenuated
by prolonged exposure to oxygen ; by exposure to a tempera-
ture a little below that which would completely destroy vitality;
by the action of certain chemica4 agents ; and in some cases,
by passing through a series of non-susceptible animals.

As a general rule pathogenic virulence is increased by suc-
cessive inoculations in susceptible animals and diminished by
cultivating the pathogenic micro-organism in artificial media
outside of the animal body or by passing it through animals
having but slight susceptibility to its pathogenic action. As
pathogenic virulence depends, to a considerable extent at least,
upon the formation of toxic substances during the active

IMMUNITY. 19

development of the pathogenic micro-organism, we infer that
diminished virulence is due to a diminished production of these
toxic substances.

An important step was made in the progress of our knowl-
edge in this field of research when it was shown that animals
may be made immune against certain infectious diseases by
inoculating them with filtered cultures, containing the toxic
substances just referred to, but free from the living bacteria
to which they owe their origin. The first satisfactory experi-
mental evidence of this important fact was obtained by Salmon
and Smith in 1886. These bacteriologists succeeded in pro-
ducing an immunity in pigeons against the pathogenic effects
of the bacillus of hog cholera, which is very fatal to these
birds, by inoculating them with sterilized cultures of the
bacillus mentioned. Similar results were reported by Roux in
1888, from the injection into susceptible animals of sterilized
cultures of the anthrax bacillus, and also of the bacillus of
symptomatic anthrax. More recently (1890) Behring and
Kitasato have shown that animals may be made immune
against the pathogenic action of the bacillus of tetanus or the
bacillus of diphtheria by the injection of filtered, germ-free
cultures of these bacilli. Similar results have been obtained
by G. and F. Klemperer (1891), in experiments upon rabbits,
with filtered cultures of the micrococcus of croupous pneu-
monia.

In Pasteur's protective inoculations against hydrophobia it
is probable that the immunity which is developed after infec-
tion by the bite of a rabid animal is due to the toxin (toxal-
bumin t) of this disease present in the emulsion of spinal cord
which is used in these inoculations.

There is also some evidence to show that a certain degree
of immunity against tuberculosis may be produced in guinea
pigs by injections of the toxic substances developed during the
growth of the tubercle bacillus, — Koch's tuberculin.

20 BIOLOGICAL LECTURES.

Explanation of Natural Immunity.

We have now to inquire upon what the natural immunity
depends which enables the healthy animal body to resist inva-
sion by the destructive agents referred to.

Phagocytosis. — In my chapter on " Bacteria in Infectious
Diseases," in Bacteria^ published in the spring of 1884, but
placed in the hands of the publishers in 1883, I say : —

** It may be that the true explanation of the immunity
afforded by a mild attack of an infectious germ disease is to
be found in an acquired tolerance to the action of a chemical
poison produced by the micro-organism, and consequent ability
to bring the resources of nature to bear to restrict invasion by
the parasite."

In the same chapter the resources of nature supposed to be
brought to bear in restricting invasion by the parasite are
referred to as follows : —

*' If we add a small quantity of culture fluid containing the
bacteria of putrefaction to the blood of an animal withdrawn
from the circulation into a proper receptacle and maintained in
a culture oven at blood-heat, we will find that these bacteria
multiply abundantly, and evidence of putrefactive decomposi-
tion will soon be perceived. But if we inject a like quantity
of the culture fluid, with its contained bacteria, into the cir-
culation of a living animal, not only does no increase and no
putrefactive change occur, but the bacteria introduced quickly
disappear, and at the end of an hour or two the most careful
microscopical examination will not reveal the presence of a
single bacterium. This difference we ascribe to the vital
properties of the fluid as contained in the vessels of a living
animal, and it seems probable that the little masses of proto-
plasm known as white blood-corpuscles are the essential histo-
logical elements of the blood, as far as any manifestation of
vitality is concerned. The writer has elsewhere (1881) sug-
gested that the disappearance of the bacteria from the circtdatioiiy
in the experiments referred tOy may be effected by the white
corpuscles, which, it is well known, pick up, after the manner

IMMUNITY. 2 1

of amoebae, any particles, organic or inorganic, which come in
their way. And it requires no great stretch of credulity to
believe that they may^ like an amceba^ digest and assimilate the
protoplasm of the captured bacterium^ thus putting an end to the
possibility of its doing any harm,.

** In the case of a pathogenic organism we may imagine
that, when captured in this way, it may share a like fate if the
captor is not paralyzed by some potent poison evolved by it, or
overwhelmed by its superior vigor and rapid multiplication.
In the latter event the active career of our conservative white
corpuscles would be quickly terminated and its protoplasm
would serve as food for the enemy. It is evident that in a
contest of this kind the balance of power would depend upon
circumstances relating to the inherited vital characteristics of
the invading parasite and of the invaded leucocyte."

This explanation is now very commonly spoken of as the
" Metschnikoff theory," although, as shown by the above
quotations, it was clearly stated by the writer several years
(1881) before Metschnikoff's first paper (1884) was published.
Metschnikoff has, however, been the principal defender of this
explanation of acquired immunity, and has made extensive
and painstaking researches, as a result of which many facts
have been brought to light which appear to give support to
the present writer's hypothesis, — the so-called Metschnikoff
theory.

The time at my disposal will not permit me to review the
experimental evidence for and against the view that phagocytosis
is the principal factor in protecting animals from invasion by
pathogenic bacteria. The conclusion which I have reached is
stated in my recently published work on Immunity^ Protective
Inoculation^ and Serum- Therapy as follows : —

"The experimental evidence submitted, considered in con-
nection with the extensive literature relating to 'phagocytosis,'
leads us to the conclusion that natural immunity is due to a
germicidal substance present in the blood-serum which has its
origin (chiefly, at least) in the leucocytes, and is soluble only
in an alkaline medium ; and that local infection is usually
resisted by an afflux of leucocytes to the point of invasion,

22 BIOLOGICAL LECTURES.

but that phagocytosis is a factor of secondary importance in
resisting parasitic invasion ; also that general infection, at
least in some infectious diseases, is resisted, and in non-fatal
cases overcome, by an increase in the number of leucocytes
and in the alkalinity of the blood-serum, — which favors solu-
tion of the germicidal proteids contained in the polynuclear
leucocytes,"

Recent researches indicate that the principal factor in the
production of acquired immunity is the presence in the blood
of the immune animal of some substance capable of neutral-
izing the toxic products of the particular pathogenic micro-
organism against which immunity exists, or of destroying the
" germ " itself.

These substances are called antitoxins. As pointed out by
Buchner in a recent paper, the antitoxins differ essentially
from the so-called alexins, to which natural immunity is
ascribed. The alexins are characterized by their germicidal
and globulicidal action (they destroy both the red corpuscles
and the leucocytes of animals belonging to a different species
from that from which they have been obtained), and by their
coagulability and instability — destroyed by sunlight and by a
temperature of 50° to 55° C. On the other hand, the anti-
toxins best known (diphtheria and tetanus) have no germicidal
or globulicidal action ; they resist the action of sunlight and
require a temperature of 70° to 80° C. for their destruction.

Our knowledge of the antitoxins dates from the experiments
made in the Hygienic Institute of Tokio, by Ogata and
Jasuhara, in 1890. These bacteriologists discovered the im-
portant fact that the blood of an animal immune against anthrax
contains some substance which neutralizes the toxic products
of the anthrax bacillus. When cultures were made in the
blood of dogs, frogs, or of white rats, which animals have a
natural immunity against anthrax, they were found not to kill
mice inoculated with them. Further experiments showed that
mice inoculated with virulent anthrax cultures did not succumb
to anthrax septicaemia if they received at the same time a sub-
cutaneous injection of the blood of an immune animal. Further,
it was found that mice which had survived anthrax infection as

IMMUNITY. 23

a result of this treatment were immune at a later date (after
several weeks), when inoculated with a virulent culture of the
anthrax bacillus. In the same year (1890) Behring and Kita-
sato discovered that the blood of an animal which has an
acquired immunity against tetanus or diphtheria, when added
to a virulent culture of one or the other of these bacilli,
neutralizes the pathogenic power of such cultures, as shown
by inoculation into susceptible animals ; and also that cultures
from which the bacilli have been removed by filtration, and
which kill susceptible animals in very small amounts, have
their toxic potency destroyed by adding to them the blood of
an immune animal, which is thus directly proved to contain an
antitoxin, — which comparative experiments show not to be
present in the blood of non-immune animals. In the experi-
ments of Behring and Kitasato referred to, it was found that
5 c.c. of serum from the blood of an immune rabbit, mixed with
I c.c. of a virulent filtrate of the tetanus bacillus, and allowed
to stand for twenty -four hours, completely neutralized its toxic
power, as shown by inoculations in mice : 0.2 c.c. of this
mixture injected into a mouse was without effect, while
0.000 1 c.c. of the filtrate, without such admixture, was infallibly
fatal to mice. The mice inoculated with this mixture remained
immune for forty or fifty days, after which they gradually lost
their immunity. The blood or serum from an immune rabbit,
when preserved in a dark, cool place, retained its power of
neutralizing the tetanus toxalbumin for about a week, after
which time it gradually lost this power. Behring and Kitasato
have also shown that the serum of a diphtheria-immune rabbit
destroys the potent toxalbumin in diphtheria cultures. It does
not, however, possess any germicidal power against the diph-
theria bacillus.

In 1 89 1 G. and F. Klemperer published an important
memoir, in which they give an account of their researches
relating to the question of immunity, etc., in animals subject
to the form of septicaemia produced by the micrococcus of
croupous pneumonia. They were able to produce immunity in
susceptible animals by introducing into their bodies filtered
cultures of this micrococcus, and proved by experiment that

24 BIOLOGICAL LECTURES.

this immunity had a duration of at least six months. They
also arrived at the conclusion that the immunity induced by
injecting filtered cultures into susceptible animals is due to the
production of an antitoxin in the body of the animal.

Brieger, Kitasato, and Wassermann have reported (1892)
their success in conferring immunity upon guinea pigs against
the pathogenic action of the cholera spirillum. They found
that attenuated cultures suitable for use as "vaccines" could
be obtained by cultivating the spirillum in bouillon made from
the thymus gland of the calf, by which means they have also
obtained attenuated cultures of the bacillus of diphtheria, the
bacillus of typhoid fever, the bacillus of tetanus and the strep-
tococcus of erysipelas. Guinea pigs inoculated with a culture
in thymus bouillon, which had been subjected to a temperature
of 65° C. for fifteen minutes, were found after twenty-four
hours to be immune against virulent cultures in twice the
amount which would otherwise have been fatal.

During the past two or three years numerous additional
experiments have been reported which confirm the results
already referred to, and show that immunity may be produced
in a similar manner against the toxic products of various other
pathogenic bacteria, — the typhoid bacillus, the " colon " bacillus,
streptococcus pyogenes, staphylococcus pyogenes aureus and
albus, etc.

The Italian investigators, Tizzoni and Centanni, in 1892,
published a preliminary communication in which they gave the
results of experiments which appear to show that in guinea
pigs treated with tuberculin, by Koch's method, a substance
is developed which neutralizes the pathogenic potency of
the tubercle bacillus. Professor Tizzoni and his associate,
Dr. Schwarz, have also (1892) obtained evidence that there is
an antitoxin of rabies. Blood-serum taken from a rabbit
having an artificial immunity against this disease was found to
neutralize in vitro the virulence of the spinal marrow of a rabid
animal after a contact of five hours. The blood-serum of dogs
having an acquired immunity against rabies was found to have
a similar action, but in much less degree. The substance
(antitoxin) present in the blood-serum of an immune rabbit

IMMUNITY. 25

does not dialyze ; it is precipitated by alcohol, and preserves
its activity, to a considerable extent, after precipitation. It is
soluble in glycerin, and is said to have the general characters
of a "globulin." The experimenters named also succeeded in
conferring immunity upon susceptible animals by injecting into
them blood-serum containing this antitoxin. According to the
Italian investigators named, the antitoxins of tetanus and of
rabies are found only in the blood-serum of immune animals,
and not in the tissues (nervous or muscular), or in the paren-
chyma of the various organs.

Professor Ehrlich, of Berlin, in 1891, published the results of
some researches which have an important bearing upon the
explanation of acquired immunity, and which show that suscepti-
ble animals may be made immune against the action of certain
toxic proteids of vegetable origin, other than those produced
by bacteria ; also that this immunity depends upon the pres-
ence of an antitoxin in the blood-serum of the immune animals.

In a later paper (1892) Ehrlich has given an account of
subsequent experiments which show that the young of mice,
which have an acquired immunity for these vegetable toxal-
bumins, may acquire immunity from the ingestion of their
mother's milk ; and also that immunity from tetanus may be
acquired in a brief time by young mice through their mother's
milk. In his tetanus experiments Ehrlich used blood-serum
from an immune horse to give immunity to the mother-mouse
when her young were already seventeen days old. Of this
blood-serum 2 c.c. was injected at a time on two successive
days. The day after the injection one of the sucklings received
a tetanus inoculation, by means of a splinter of wood to which
spores were attached. The animal remained in good health,
while a much larger control mouse, inoculated in the same way,
died of tetanus at the end of twenty-six hours. Other suck-
lings, inoculated at the end of forty-eight hours and of seventy-
two hours after the mother had received the injection of blood-
serum, likewise remained in good health, while the control
mice died.

The possibility of conferring immunity by means of the milk
of an immune animal is further shown by the experiments of

26 BIOLOGICAL LECTURES.

Brieger and Ehrlich (1892). A female goat was immunized
against tetanus by the daily injection of "thymus tetanus
bouillon." The dose was gradually increased from 0.2 c.c. to
10 c.c. At the end of thirty-seven days a mouse, which
received o.i c.c. of the milk of this goat in the cavity of the
abdomen, proved to be immune against tetanus. Further
experiments gave a similar result, even when the milk of the
goat was not injected into the peritoneal cavity of the mouse
until several hours after inoculation with a virulent culture of
the tetanus bacillus.

In a subsequent communication (1893) Brieger and Ehrlich
describe their method of obtaining the antitoxin of tetanus
from milk in a more concentrated form. They found by experi-
ment that it was precipitated by ammonium sulphate and mag-
nesium sulphate. From twenty-seven to thirty per cent of
ammonium sulphate added to milk caused a precipitation of
the greater part of the antitoxin. This precipitate was dis-
solved in water, dialyzed in running water, then filtered and
evaporated in shallow dishes at 35° C. in a vacuum. One liter
of milk from an immune goat gave about i gm. of a trans-
parent, yellowish-white precipitate, which contained fourteen
per cent of ammonium sulphate. This precipitate had from
four hundred to six hundred times the potency of the milk
from which it was obtained in neutralizing the tetanus toxin.

A most interesting question presents itself in connection
with the discovery of the antitoxins. Does the animal which
is immune from the toxic action of any particular toxalbumin
also have an immunity for other toxic proteids of the same
class } The experimental evidence on record indicates that it
does not. In Ehrlich's experiments with ricin and abrin he
ascertained that an animal which had been made immune
against one of these substances was quite as susceptible to the
toxic action of the other as if it did not possess this immunity, —
i.e. the antitoxin of ricin does not destroy abrin, and vice versa.
As an illustration of the fact he states that in one experiment
a rabbit was made immune for ricin to such an extent that the
introduction into its eye of this substance in powder produced
no inflammatory reaction ; but the subsequent introduction of

IMMUNITY. 2 7

a solution of abrin, of i to 10,000, caused a violent inflam-
mation. In this connection we may remark that there is
some evidence to show that persons who are repeatedly stung
by certain poisonous insects — mosquitoes, bees — acquire a
greater or less degree of immunity from the distressing local
effects of their stings.

We have also experimental evidence that animals may
acquire a certain degree of immunity from the toxic action of
the venom of the rattlesnake. This was first demonstrated by
Sewall {1887), and has been recently confirmed by Calmette

(1894).

The experimental evidence recorded justifies the conclusion
that in the diseases referred to acquired immunity depends,
chiefly at least, upon the presence of a peculiar proteid sub-
stance in the blood of the immune animal — antitoxin —
which neutralizes the toxic substance — toxin or toxalbumin
— to which the morbid phenomena which characterize the
disease are due.

But it would be premature to infer that in all infectious
diseases immunity depends upon the production of an antitoxin
in the blood of the immune animal. Indeed, we have experi-
mental evidence which shows that in certain cases the blood-
serum of immune animals has no antitoxic power, but acts
upon the germ itself, instead of upon its toxic products.

It may be worth while to refer briefly, before closing, to
some examples of acquired immunity of a different order. We
refer to the tolerance of extremes of heat and cold which may
be established by habitual exposure, and more especially to the
tolerance to narcotics and irritant poisons, which is very
remarkable, and has never been explained in a satisfactory
manner. A recent writer (Samuel, 1892) has presented experi-
mental evidence which shows that the local inflammation which
results from the application of croton oil to the ear of a rab-
bit does not occur when a second application is made to the
same ear after recovery from the effects of the first. That a
tolerance may be acquired to comparatively large doses of
arsenic is well known, and the tolerance which the victims of
drug habits acquire to enormous doses of narcotics is a matter

28 BIOLOGICAL LECTURES.

of daily observation. In the writer's paper on acquired immu-
nity, published in i88r, an attempt is made to account for
acquired immunity in infectious diseases as analogous to the
immunity to drugs just referred to. But it is evident that in
the present state of science the analogy is incomplete, and
possibly delusive, in the absence of any experimental evidence
of the presence of specific antitoxins in the blood of those who,
as a result of habit, tolerate excessive doses of morphia, cocaine,
narcotin, etc.

THIRD LECTURE.

A STUDENT'S REMINISCENCES OF HUXLEY.

HENRY FAIRFIELD OSBORN.

(Columbia College, N. Y.)

By far the larger number of American students who go
abroad pass through the English Channel, obtain a distant
view of the mother country, and after from one to three years
in Germany, return with an exclusively German education.
Having visited neither England nor France, the implication
is that the countries which produced Owen, Darwin, Huxley,
Balfour, or Lamarck, Cuvier, St. Hilaire, and Pasteur have
nothing to offer the American student. But this is not the
fact. The fact is that England and France are a half-century
behind Germany in that kind of university organization which
attracts a foreign student, and enables him immediately to find
his level and enter upon his research. English and French
universities until a very recent date have been either not so
fully prepared, or have met the newcomer with practically
insuperable obstacles in the matter of a degree.

None the less, the student who has not breasted these
obstacles for the compensating advantages which the English
and French schools offer has made a serious mistake. He has
brought back not an Old World education, but an exclusively
German education, with its splendidly sound and unique
features, and with many inherent defects. Germany produces
the generals and the rank and file of the armies of science,
but certainly the commanders-in-chief, in biology at least, have
been Englishmen. If we find the highest exponents of purely
inductive research in Germany, we certainly find a better union

30 BIOLOGICAL LECTURES.

of the inductive and deductive methods in France and England.
France leads in expression and style of thought, although, upon
the whole, less sound in substance than Germany. England,
and France in her best period, have given us the most far-
reaching and permanent generalizations in biology. It follows
that the American student who can afford the experience will
profit most by placing himself successively in the scientific
atmosphere of Germany, France, and England. My own post-
graduate education was unfortunately not of this three-sided
type. None the less, it has always seemed a most fortunate
circumstance that in the spring of 1879 a letter from the vener-
able Kitchen Parker led me to Cambridge, and to the great
privilege of sitting under Balfour, the most brilliant and lovable
of men. In the following autumn Huxley's lectures upon
Comparative Zoology began in October, and by entering this
course I came to know personally this great master, and
through him enjoyed the rare opportunity of meeting Charles
Darwin. After this experience, which was equally open to any
serious student of biology at that time, it is natural that I
should strongly advise those of you who are planning your
foreign studies to spend part of your time in England, and
endeavor to discern some of the distinctive qualities of English
men of science which Huxley so nobly illustrated. You will
pardon the personal element in the following recollections of
Huxley as a teacher, and the rather informal review of his life
work.

Huxley, as a teacher, can never be forgotten by any of his
students. He entered his lecture-room promptly as the clock
was striking nine, rather quickly, and with his head bent forward
*' as if oppressive with its mind." He usually glanced attention
to his class of about ninety, and began speaking before he
reached his chair. He spoke between his lips, but with per-
fectly clear analysis, with thorough interest, and with philo-
sophic insight which was far above the average of his students.
He used very few charts, but handled the chalk with great
skill, sketching out the anatomy of an animal as if it were a
transparent object. As in Darwin's face, and as in Erasmus
Darwin's or Buffon's, and many other anatomists with a strong

A STUDENT'S REMINISCENCES OF HUXLEY,

31

sense of form, his eyes were heavily overhung by a projecting
forehead and eyebrows, and seemed at times to look inward.
His lips were firm and closely set, with the expression of posi-
tiveness, and the other feature which most marked him was
the very heavy mass of hair falling over his forehead, which he
would frequently stroke or toss back. Occasionally he would
lighten up the monotony of anatomical description by a bit of
humor. I remember one instance which was probably reminis-
cent of his famous tilt with Bishop Wilberforce at the meeting
of the British Association in i860. Huxley was describing
the mammalian heart, and had just distinguished between the
tricuspid valve on the right side of the heart and the bicuspid
valve on the left, which you know resembles a bishop's miter,
and hence is known as the mitral valve. He said, " It is not
easy to recall on which side these respective valves are found,
but I recommend this rule : you can easily remember that the
mitral is on the left, because a bishop is never known to be on
the right."

Huxley was the father of modern laboratory instruction ; but
in 1879 h^ "^^s so intensely engrossed with his own researches
that he very seldom came through the laboratory, which was
ably directed by T. Jeffrey Parker, assisted by Howes and
W. Newton Parker, all of whom are now professors, Howes
having succeeded to Huxley's chair. Each visit, therefore,
inspired a certain amount of terror, which was really unwar-
ranted, for Huxley always spoke in the kindest tones to his
students, although sometimes he could not resist making fun
at their expense. There was an Irish student who sat in front
of me, whose anatomical drawings in water color were certainly
most remarkable productions. Huxley, in turning over his
drawing-book, paused at a large blur, under which was carefully
inscribed, "sheeps' liver," and smilingly said, "I am glad to
know that is a liver ; it reminds me as much of Cologne
cathedral in a fog as of anything I have ever seen before."
Fortunately the nationality of the student enabled him to fully
appreciate the humor.

The greatest event in the winter of 1879 was Darwin's first
and only visit to the laboratory. They came in together.

32 BIOLOGICAL LECTURES.

Huxley leading slowly down the long narrow room, pointing
out the especial methods of teaching which he had originated
and which are now universally adopted in England and in this
country. Darwin was instantly recognized by the class as he
entered, and a thrill of curiosity passed down the room, for no
one present had ever even seen him before. I remember my own
feelings very distinctly. I was just finishing a laborious dissec-
tion of the lobster's nervous system, and out of politeness and
deference to laboratory discipline, pretended to continue my
work, with results fatal to the nervous system of the crustacean.
As the pair came back up the room Huxley singled me out, I
suppose because I was the only foreign student, and introduced
me to Darwin, — the greatest kindness he could have shown a
young student. There was the widest possible contrast in the
two faces. Darwin's grayish- white hair and bushy eyebrows
overshadowed the pair of deeply set blue eyes, which seemed
to image his wonderfully calm and deep vision of nature, and
at the same time to emit benevolence. Huxley's piercing
black eyes and determined and resolute face were full of
admiration and at the same time protection of his older friend.
He said afterwards : " You know I have to take care of him —
in fact, I have always been Darwin's bull-dog," and this exactly
expressed one of the many relations which existed so long
between the two men.

Huxley was not always fortunate in the intellectual caliber
of the men to whom he lectured in the Royal School of Mines.
Many of the younger generation were studying in the univer-
sities, under Balfour at Cambridge and under Rolleston at
Oxford. However, Saville Kent, C. Lloyd Morgan, George B.
Howes, T. Jeffrey Parker, and W. Newton Parker are repre-
sentative biologists who were wholly trained by Huxley. Many
others, not his students, have expressed the deepest indebted-
ness to him. Among these, especially, are Prof. E. Ray
Lankester, of Oxford, and Prof. Michael Foster, of Cambridge.
Huxley once said that he had *' discovered Foster." He not
only singled men out, but knew how to direct and inspire them
to investigate the most pressing problems of the day. As it
was, his thirty-one years of lectures would have produced a far

A STUDENT'S REMINISCENCES OF HUXLEY. 33

greater effect if they had been delivered from an Oxford, Cam-
bridge, or Edinburgh chair. In fact, Huxley's whole life would
have been different, in some ways more effective, in others
less so, if the universities had welcomed the young genius
who was looking for a post, and even cast his eyes toward
America in 1850; but in those early days of classical prestige
both seats of learning were dead to the science, which it was
Huxley's great service in support of Darwin to place beside
physics, in the lead of all others in England. Moreover,
Oxford, if not Cambridge, could not long have sheltered such
a wolf in the fold.

Huxley's public addresses always gave the impression of
being largely impromptu ; but he once told me : " I always
think out carefully every word I am going to say. There is
no greater danger than the so-called inspiration of the moment^
which leads you to say something which is not exactly true, or
which you would regret afterward. I sometimes envy your
countrymen their readiness, and believe that a native Ameri-
can, if summoned out of bed at midnight, could step to his
window and speak well upon any subject." I told him I feared
he had been slightly misinformed. I feared that many Ameri-
can impromptu speeches were more distinguished by a flow of
language than of ideas. But Huxley was sometimes very
impressive when he did not speak. In 1879 ^^ ^^^ strongly
advocating the removal of the Royal School of Mines from
crowded Jermyn Street to South Kensington, — a matter which
is still being agitated. At a public dinner given by the alumni
of the school, who were naturally attached to the old buildings,
the chairman was indiscreet enough to make an attack upon
the policy of removal. He was vigorously applauded, when, to
every one's consternation, Huxley, who was sitting at the
chairman's right, slowly rose, paused a moment, and then
silently skirted the tables and walked out of the hall. A
solemn pall fell over the remainder of the dinner, and we were
all glad to find an excuse to leave early.

In personal conversation Huxley was full of humor and
greatly enjoyed stories at his own expense. Such was the fol-
lowing : ** In my early period as a lecturer, I had very little

34 BIOLOGICAL LECTURES.

confidence in my general powers, but one thing I prided my-
self upon was clearness. I was once talking of the brain
before a large, mixed audience, and soon began to feel that no
one in the room understood me. Finally I saw the thoroughly
interested face of a woman auditor, and took consolation in
delivering the remainder of the lecture directly to her. At
the close, my feeling as to her interest was confirmed when
she came up and asked if she might put one question upon a
single point which she had not quite understood. * Certainly,'
I replied. ' Now Professor,' she said, * is the cerebellum inside
or outside of the skull .?' " Once, speaking of his deafness, he
said : '' It is a great misfortune to be deaf in only one ear.
Every time I dine out, the lady sitting by my good ear thinks
I am charming, but I make a mortal enemy of the lady on my
deaf side." A story of his about babies is also characteristic :
''When a fond mother calls upon me to admire her baby I
never fail to respond ; and, while cooing appropriately, I take
advantage of an opportunity to gently ascertain whether the
soles of its feet turn in and tend to support my theory of
arboreal descent."

Huxley's life is as full of suggestion to the student as were
his lectures and his conversation. It illustrates the force of
obtaining a very broad view of the animal kingdom before we
attempt to enter the plane of higher generalization. Huxley's
training in embryology, vertebrate and invertebrate zoology,
palaeontology, and geology was not mapped out for him as
for the modern university student. His prolonged sea-voyage
gave him time and material for reflection, and after this he
was led from one subject to another until he obtained a grasp
of nature as a whole, second only to that of Darwin.

Huxley was born in 1825. Like Goethe, he inherited from
his mother his brilliantly alert powers of thought, and from his
father, his courage and tenacity of purpose, — a combination of
qualities which especially fitted him for the period in which he
was to live. There is nothing striking recorded about his boy-
hood as a naturalist. He preferred engineering, but was led
into medicine.

At the close of his medical course he secured a navy medical

A STUDENT'S REMINISCENCES OF HUXLEY. 35

post upon the " Rattlesnake." This brought with it, as to
Darwin, the training of a four-years' voyage to the South Seas
off eastern Australia and west Guinea — a more liberal educa-
tion to a naturalist than any university affords, even at the
present day. This voyage began at twenty-one, and he says of
it : " But, apart from experience of this kind and the oppor-
tunity offered for scientific work to me, personally, the cruise
was extremely valuable. It was good for me to live under
sharp discipline, to be down on the realities of existence by
living on bare necessities, to find out how extremely worth
living life seemed to be, when one woke from a night's rest on
a soft plank, with the sky for a canopy, and cocoa and weevily
biscuit the sole prospect for breakfast, and more especially to
learn to work for what I got for myself out of it. My brother
officers were as good as sailors ought to be and generally are ;
but, naturally, they neither knew nor cared anything about my
pursuits, nor understood why I should be so zealous in the
pursuit of the objects which my friends, the middies, christened
'Buffons,' after the title conspicuous on a volume of the Suites
a Biiffon, which stood in a prominent place on my shelf in the
chart-room."

As a result of this voyage of four years, numerous papers
were sent home to the Linnaean Society, of London, but few
were published. Upon his return, his first work. Upon the
Anatomy and Affinities of the Medusce^ was declined for publica-
tion by the Admiralty — a fortunate circumstance, for it led to
his quitting the navy for good and trusting to his own re-
sources. Upon publication (1849) this memoir at once estab-
lished his scientific reputation at the early age of twenty-four,
just as Richard Owen had won his spurs by his Memoir on
the Pearly Nautilus. In 1852 Huxley's preference as a biolo-
gist was to turn back to physiology, which had become his
favorite study in the medical course. But his fate was to enter
and become distinguished in a widely different branch, which had
as little attraction for him as for most students of marine life,
namely, palaeontology. He says of this sudden change of base :

'*At last, in 1854, on the translation of my warm friend
Edward Forbes to Edinburgh, Sir Henry de la Beche, the

36 BIOLOGICAL LECTURES.

Director-General of the Geological Survey, offered me the post
Forbes had vacated of Palaeontologist and Lecturer on Natural
History. I refused the former point-blank, and accepted the
latter only provisionally, telling Sir Henry that I did not care
for fossils, and that I should give up natural history as soon as
I could get a physiological post. But I held the office for
thirty-one years, and a large part of my work has been palae-
ontological."

From this time until 1885 his labors extended over the
widest field of biology and of philosophy ever covered by any
naturalist, with the single exception of Aristotle. In philos-
ophy Huxley showed rare critical and historical power. He
made the most exhaustive study of Hume, but his own philo-
sophical spirit and temper was more directly the offspring of
Descartes. Some subjects he mastered, others he merely
touched ; but every subject which he wrote about he illumi-
nated. Huxley did not discover or first define protoplasm, but
he made it known to the English-speaking world as the physical
basis of life — recognizing the unity of animal and plant proto-
plasm. He cleared up certain problems among the Protozoa.
In 1849 appeared his great work upon the oceanic Hydrozoa^
and familiarity with these forms doubtless suggested the bril-
liant comparison of the two-layered gastrula to the adult
hydrozoa. He threw light upon the Tunicata, describing the
endostyle as a universal feature, but not venturing to raise the
Tunicata to a separate order. He set in order the cephalopod
mollusca, deriving the spiral from the straight-shelled fossil
forms. He contributed to the Arthropoda, his last word upon
this group being his charming little volume upon the Cray-
fish,— a model of its kind. But think of the virgin field which
opened up before him among the vertebrata, when in 1859 he
was the first to perceive the truth of Darwin's theory of descent.
Here were Cuvier's and Owen's vast researches upon living and
extinct forms, a disorderly chaos of facts waiting for generali-
zation. Huxley was the man for the time. He had already
secured a thoroughly philosophical basis for his comparative
osteology by studying the new embryology of Von Baer, which
Richard Owen had wholly ignored. In 1858 his famous

A STUDENT'S REMINISCENCES OF HUXLEY. 37

Croonian lecture on the "• Theory of the Vertebrate Skull "
gave the deathblow to Owen's life-work upon the skull and
vertebral archetype, and to the whole system of mystical and
transcendental anatomy ; and now Huxley set to work vigor-
ously to build out of Owen's scattered tribes the great limbs
and branches of the vertebrate tree. He set the fishes and
batrachia apart as the Icthyopsidan branch, the reptiles and
birds as the Satcropsidan in contrast with the Mammalian^
which he derived from a pro-sauropsidan or amphibian stem, —
,a theory which, with some modification, has received strong
recent verification.

Professor Owen, who had held undisputed sway in England
up to 1858, fought nobly for opinions which had been idolized
in the first half-century, but was routed at every point. Hux-
ley captured his last fortress when, in his famous essay of
1865, "Man's Place in Nature," he undermined Owen's teach-
ing of the separate and distinct anatomical position of man.
We can only appreciate Huxley's fighting-qualities when we
see how strongly Owen was intrenched at the beginning of
this long battle royal. He was director of the British Museum,
and occupied other high posts ; he had the strong moral sup-
port of the government and of the royal family, although these
were weak allies in a scientific encounter.

Huxley's powers of rapid generalization of course betrayed
him frequently. His Bathybius was a groundless and short-
lived hypothesis ; he went far astray upon the phylogeny of
the horses. But these and other errors were far less attribu-
table to defects in his reasoning powers than to the extraordi-
narily high pressure under which he worked for the twenty
years between i860 and 1880, when duties upon the Educa-
tional Board, upon the Government Fisheries Commission,
and upon Parliamentary committees crowded upon him. He
had at his command none of the resources of modern tech-
nique. He cut his own sections. I remember once seeing
some of his microscopic sections. To one of our college
junior students working with a Minot microtome Huxley's
sections would have appeared like a translucent beefsteak,
— another illustration that it is not always the section

38 BIOLOGICAL LECTURES.

which reveals the natural law, but the man who looks at the
section.

Huxley was not only a master in the search for truth, but in
the way in which he presented it, both in writing and in speak-
ing ; and we are assured, largely as he was gifted by nature,
his beautifully lucid and interesting style was partly the result
of deliberate hard work. He was not born to it ; some of his
early essays are very labored. He acquired it. He was familiar
with the best Greek literature, and restudied the language. He
pored over Milton and Carlyle and Mill. He studied the fine
old English of the Bible. He took as especial models Hume
and Hobbes, until finally he wrote his mother tongue as no
other Englishman wrote it. Take up any one of his essays, —
biological, literary, philosophical; you at once see his central idea
and his main purpose, although he never uses italics or spaced
letters as many of our German masters do to relieve the
obscurity of their sentences. We are carried along upon the
broad current of his reasoning without being confused by his
abundant side illustrations. He gleaned from the literature of
all time until his mind was stocked with apt similes. Who but
Huxley would have selected the title " Lay Sermons " for his
first volume of addresses; or, in 1880, twenty-one years after
Darwin's work appeared, would have entitled his essay upon
the influence of this work, "■ The Coming of Age of the Origin
of Species" .? Or to whom else would it have occurred to repeat
over the grave of Balfour the exquisitely appropriate lines : —

" For Lycidas is dead, dead ere his prime,
Young Lycidas, and hath not left his peer."

Who else could have inveighed thus against modern specializa-
tion : " We are in the case of Tarpeia, who opened the gates of
the Roman citadel to the Sabines and was crushed by the weight
of the reward bestowed upon her. It has become impossible
for any man to keep pace with the progress of the whole of
any important branch of science. It looks as if the scientific,
like other revolutions, meant to devour its own children ; as if
the growth of science tended to overwhelm its votaries ; as
if the man of science of the future were condemned to diminish

A ST (/DENT'S REMINISCENCES OF HUXLEY. 39

into a narrower specialist as time goes on. It appears to me
that the only defence against this tendency to the degeneration
of scientific workers lies in the organization and extension of
scientific education in such a manner as to secure breadth of
culture without superficiality."

What Haeckel did for evolution m Germany, Huxley did in
England. As the earliest and most ardent supporter of Darwin
and the theory of descent, it is remarkable that he never gave
an unreserved support to the theory of natural selection as all-
sufficient. Twenty-five years ago, with his usual penetration
and prophetic insight, he showed that the problem of variation
might, after all, be the greater problem ; and only three years
ago, in his " Romanes Lecture," he disappointed many of the
disciples of Darwin by declaring that natural selection failed to
explain the origin of our moral and ethical nature. Whether
he was right or wrong we will not stop to discuss, but consider
the still more remarkable conditions of Huxley's relations to
the theory of evolution. As expositor, teacher, defender, he
was the high priest of evolution. From the first, he saw the
strong and weak points of the special Darwinian theory. He
wrote upon the subject for thirty years, and yet he never con-
tributed a single original or novel idea to it ; in other words,
Huxley added vastly to the demonstration, but never added to
the sum of either theory or working hypothesis, and the con-
temporary history of the theory proper could be written with-
out mentioning his name. This lack of speculation upon the
factors of evolution was true throughout his whole life. In the
voyage of the " Rattlesnake " he says he did not even think of
the species problem. His last utterance regarding the causes of
evolution appeared in one of the Reviews as a passing criticism
of Weismann's finished philosophy, in which he implies that his
own philosophy of the causes of evolution was as far off as
ever ; in other words, Huxley never fully made up his mind or
committed himself to any causal theory of development.

Taking the nineteenth century at large, outside of our own
circles of biology, Huxley's greatest and most permanent
achievement was his victory for free thought. Personally we
may not be agnostic ; we may disagree with much that he has

40 BIOLOGICAL LECTURES.

said and written, but we must admire Huxley's valiant services
none the less. A reformer must be an extremist, and Huxley
was often extreme, but he never said what he did not believe to
be true. If it is easy for you and for me to say what we think
in print and out of print now, it is because of the battles fought
by such men as Huxley and Haeckel. When Huxley began his
great crusade, the air was full of religious intolerants and, what
is quite as bad, scientific shams. If Huxley had entered the
contest carefully and guardedly, he would have been lost in the
enemy's ranks ; but he struck right and left with sledge-hammer
blows, whether it was a high dignity of the Church or of the
State. Just before the occasion of one of his greatest contests,
that with Gladstone in the pages of the Contemporary Review,
Huxley was in Switzerland completely broken down in health,
and suffering from torpidity of the liver. Gladstone had written
one of his characteristically brilliant articles upon the close cor-
respondence between the Order of Creation as revealed in the
first chapter of Genesis and the Order of Evolution as shown
by modern biology. "When this article reached me," Huxley
told me, " I read it through, and it made me so angry that I
believe it must have acted upon my liver. At all events, when
I finished my reply to Gladstone I felt better than I had for
months past."

Huxley's last public appearance was at the meeting of the
British Association at Oxford. He had been very urgently
invited to attend, for exactly a quarter of a century before the
Association had met at Oxford, and Huxley had had his famous
encounter with Bishop Wilberforce. It was felt that the anni-
versary would be an historic one, and incomplete without his
presence, and so it proved to be. Huxley's especial duty was
to second the vote of thanks for the Marquis of Salisbury's
address, — one of the invariable formalities of the opening
meeting of the Association. The meeting proved to be the
greatest one in the history of the Association. The Sheldonian
theatre was packed with one of the most distinguished scientific
audiences ever brought together, and the address of the Marquis
was worthy of the occasion. The whole tenor of it was the
unknown in science. Passing from the unsolved problems of

A STUDENT'S REMINISCENCES OF HUXLEY. 41

astronomy, chemistry, and physics, he came to biology. With
delicate irony he spoke of the " comforting word, evolution," and
passing to the Weismannian controversy, implied that the dia-
metrically opposed views so frequently expressed nowadays
threw the whole process of evolution into doubt. It was only
too evident that the Marquis himself found no comfort in
evolution, and even entertained a suspicion. as to its proba-
bility. It was well worth the whole journey to Oxford to
watch Huxley during this portion of the address. In his red
doctor-of-laws gown, placed upon his shoulders by the very
body of men who had once referred to him as "a Mr. Huxley,"
he sank deeper into his chair upon the very front of the plat-
form and restlessly tapped his foot. His situation was an
unenviable one. He had to thank an ex-Prime Minister of
England, and present Lord-Chancellor of Oxford University,
for an address the sentiments of which were directly against
those he himself had been maintaining for twenty-five years.
He said afterward that when the proofs of the Marquis'
address were put into his hands the day before, he realized that
he had before him a most delicate and difficult task. Lord
Kelvin (Sir William Thompson), one of the most distinguished
living physicists, first moved the vote of thanks ; but his recep-
tion was nothing to the tremendous applause which greeted
Huxley in the heart of that university whose cardinal princi-
ples he had so long been opposing. Considerable anxiety had
been felt by his friends lest his voice would fail to fill the
theatre, for it had signally failed during his Romanes Lecture
delivered in Oxford the year before ; but when Huxley arose he
reminded you of a venerable gladiator returning to the arena
after years of absence. He raised his figure and his voice to
its full height, and with one foot turned over the edge of the
step, veiled an unmistakable and vigorous protest in the most
gracious and dignified speech of thanks.

Throughout the subsequent special sessions of this meeting
Huxley could not appear. He gave the impression of being
aged but not infirm, and no one realized that he had spoken
his last word as champion of the law of Evolution. He soon
returned to Eastbourne. Early in the winter he contracted

42 BIOLOGICAL LECTURES.

the grippe, which passed into pneumonia. He rallied once or
twice, and his last effort to complete a reply to Balfour's
"■ Foundations of Belief " hastened his death, which came upon
June 29, at the age of seventy.

I have endeavored to show in how many ways Huxley was a
model for us of the younger generation. In the central hall of
the British Museum of Natural History sits in marble the life-
size figure of Charles Darwin. Upon his right will soon be
placed a beautiful statue of Richard Owen ; and I know that
there are many who will enjoy taking some share in the
movement to complete this group with the noble figure of
Thomas Henry Huxley.

FOURTH LECTURE.

PALAEONTOLOGY AS A MORPHOLOGICAL
DISCIPLINE.

PROF. W. B. SCOTT.
(Princeton University, Princeton, N.J.)

The day has forever gone by when any one mind, however
profound and comprehensive, can take all knowledge for its
province. Increase of knowledge, like advance of civilization,
necessarily brings with it a division of labor, and each of the
great branches of science becomes more and more minutely
divided and subdivided for the purposes of investigation. Such
subdivision greatly enhances the efficiency of the individual
worker, enabling him to concentrate his attention upon some
definite problem of more or less limited scope, and, so far, it is
advantageous. On the other hand, like most human devices,
it has its drawbacks, and what is gained in one direction is apt
to be lost in another. One great and growing evil is the sub-
division of knowledge which accompanies specialization of
research. The worker finds the greatest difficulty in keeping
abreast of all that is being accomplished by fellow laborers in
his own field ; how, then, shall he find time to learn anything
of the work in other fields } Not to do so involves the penalty
of such a narrowness of view as will inevitably lessen the value
of his own work, because deductions drawn legitimately enough
from a single line of investigation often appear absurd when
tested by a wider range of facts. Many a blunder might be
avoided were the worker's vision not so strictly limited by the
boundaries of his own speciality.

The narrowing effects of this subdivision of knowledge
result in a more or less marked loss of sympathy and mutual

44 BIOLOGICAL LECTURES.

understanding between the representatives of the different
branches of the same science. To magnify one's own office is
a very human infirmity, but it involves a minimizing of the
offices of others. Science is not advanced by the sneers of its
representatives at one another as mere '' species-makers," or
*' section-cutters," or "closet-naturalists," as the case may be.
One is prone to regard with instinctive distrust results which
run counter to cherished convictions, or which ill harmonize
with prevalent theories and call for a radical readjustment of
opinion. Naturally, the investigator is apt to place undue
reliance upon the methods with which he is familiar and to
undervalue other ways of attacking the same problem. Evidence
derived from other lines of investigation means less to him and
is the more readily overlooked and ignored. Perhaps the
greatest danger which at present threatens the healthy growth
of zoological science in all its branches is the ever-increasing
tendency to ambitious speculation, founded upon the narrowest
basis of fact. So much of a theoretical taint attaches to nearly
all morphological work, as to cause hesitation in fully accepting
it, and one often feels in reading that we have gone back to
the days of the transcendental anatomists. The glib use of
phrases and formulae, which hide ignorance under the guise of
"explanations" which do not explain, is an outgrowth of the
same tendency. It is the fashion to measure with elastic stand-
ards, which expand and contract to meet the needs of each
case. Dogmatism and narrow-mindedness have ever been
closely akin.

The obvious corrective for many of these evils is to take a
wider view of our subject, and for each of us to learn some-
thing of the methods and results of workers in other fields than
our own. I wish to invite your attention to a branch of mor-
phology, the bearings of which are much misapprehended by the
representatives of other departments of the same science, and
which, where not completely ignored, is often wofully abused,
namely, the subject of palaeontology. This science has too long
been abandoned to the geologist, but morphologists are coming to
see that they have an interest in it, and sometimes condescend
to make use of such parts of its data as favor their opinions.

PALEONTOLOGY AS A DISCIPLINE.

45

Even yet, however, the necessary and close connection which
obtains between palaeontology and geology leads many to the
assumption that its relation to morphology is, at best, very
remote ; but this assumption is quite unjustified, and proceeds
from a confounding of the two quite distinct aspects and offices
of palaeontology. One of these offices is to determine the
chronological succession of the rocks, and in this morphology
is very indirectly concerned ; but the other office is the study
of fossils as organisms, and here Huxley's dictum thoroughly
applies : "The only difference between a collection of fossils
and one of recent animals is that one set has been dead some-
what longer than the other." This is a shining example of the
**true word spoken in jest."

The great problems of morphology are the same for all
workers in that science ; it is the method of attacking them
which differs. If I may be allowed to quote what I have else-
where said, I would again call attention to the very instructive
character of the analogies which exist between the history,
aims, and methods of animal morphology and those of com-
parative philology. '' In both sciences the attempt is made
to trace the development of the modern from the ancient, to
demonstrate the common origin of things now widely separated
and differing in all apparent characteristics, and to establish
the modes in which, and the factors or causes by which, this
solution and differentiation have been effected. At the present
time morphology is still far behind the science of language
with regard to the solution of many of these kindred problems,
and can hardly be said to have advanced beyond the stage which
called forth Voltaire's famous sneer: " L' Etymologic est une
science ou les voyelles ne font rien et les consonnes fort peu
de chose." Of the animal pedigrees, now so frequently pro-
pounded, few have any better foundation than the guessing
etymologies of the last century, and for exactly the same
reason. Just as the old etymologists had no test to distinguish
a true derivation from a false one, except a likeness in sound
and meaning in the words compared, so the modern morpholo-
gist is yet without any sure test of the relationships of animals,
except certain likenesses or unlikenesses of structure. How

46 BIOLOGICAL LECTURES.

much weight is to be allowed a given similarity, and how far
this is offset by a dissimilarity which accompanies it, we have,
as yet, few means of determining, and have still to discover
those laws of organic change which shall render the same
service to morphology as Grimm's law has done to the study of
the Aryan tongues."

Philology was raised to the dignity of a true science by the
laborious tracing back of modern words, step by step, to their
ancient origins through all their intermediate gradations, and
sound principles of etymology could not be established until
this was done. Morphology must profit by this lesson and
must imitate the method of the science of language. Not
until many long phylogenetic series have been recovered can
the law of change be worked out. It is just here that palae-
ontology is fitted to render invaluable services to the common
cause.

As every one is aware, the principal methods of morphological
inquiry are comparative anatomy, embryology, and palaeon-
tology, each of which has its great advantages, but accom-
panied by its own peculiar drawbacks and limitations. Lack
of time will prevent any discussion of Bateson's proposed new
method from the study of variation. I have elsewhere exam-
ined that at some length.

The foundation and corner-stone of the whole structure of
morphology must ever be comparative anatomy, an accurate
knowledge of which is indispensable to successful prosecution
of the other departments of inquiry. This method has, in the
hands of the masters, registered many great triumphs in the
solution of difficult problems of homology, and of the mutual
relationships of animal groups. At the present time, the ten-
dency is to give more and more weight to its determinations.
On the other hand, finality cannot be reached by this method.
It suffers from the very significant drawback of possessing no
sure criterion by which to distinguish between those similarities
of structure which result from actual genetic relationship and
those which are due to parallel or convergent development, and
thus to determine the taxonomic value of a given likeness or
unlikeness. It is an exceedingly common fallacy to assume

PALEONTOLOGY AS A DISCIPLINE. 47

that because a number of allied groups display a certain struc-
ture, their common ancestor must also have possessed it.
This may have been the case, but it is almost as likely not to
have been, because the structure in question may have been
many times independently acquired. While the comparative
method frequently enables us to discriminate between the two
classes of phenomena, it generally does not do so, and it never
can give entire certainty upon this point.

On comparing the humerus of the horses with that of the
camels, we find in each a characteristic difference from other
artiodactyls and perissodactyls and agreement with each other, —
a feature which may be described in brief as the duplicity of
the bicipital groove and presence of a bicipital tubercle. It is
a priori probable that such an isolated resemblance between
two widely separated groups is due to convergence, and yet
the comparative method can give us no assurance that this is
not a primitive ungulate character retained in these two series
and lost in the others. Having recovered the various extinct
genera of both these phyla, we may trace out the gradual trans-
formation of the humerus and definitely show that the resem-
blance has been independently acquired at a comparatively late
period and is not a case of a persistent primitive feature.

In short, the difficulty of reaching firmly fixed conclusions
upon questions of homology and relationship by the exclusive
use of comparative anatomy lies in the fact, that this method
deals only with the modern assemblage of animals, a mere
fragment of that which has existed in former times. It is like
attempting to work out the etymology of a language which has
no literature to register its changes.

The second method of morphological inquiry, embryology,
has had a somewhat chequered career. Not many years ago it
was universally regarded as the infallible test of morphological
theory and the principle that the ontogeny repeated the
phylogenetic history in abbreviated form was accepted, almost
without question, as a fundamental law. But this view has
fallen somewhat into discredit. The admission which very
early had to be made, that " cenogenetic " features of develop-
ment were imposed upon or substituted for those due to

48 BIOLOGICAL LECTURES,

ancestral inheritance, opened the door to an unduly subjective
way of dealing with embryological evidence and deprived the
method of that authoritative character which had so generally
been ascribed to it. Now the whole recapitulation theory is
boldly called in question, and, in the admirable lecture delivered
last year in this place, Prof. E. B. Wilson showed the untrust-
worthy nature of the embryological criterion of homology. The
difficulty in this case lies in the absence of any " canons of
interpretation " (to use Bateson's phrase) by which the con-
tradictory data of embryology may be harmonized into a con-
sistent whole. To take a concrete illustration : The ontogenetic
development of the horse's teeth would give us a very inade-
quate and indeed false conception of the actual steps of change
by which the modern type of dentition has been attained, nor
would embryology show that the horse is descended from five-
toed ancestors. Knowing, as we do from the fossils, the
phyletic series, the embryological facts may be readily under-
stood. It is an undue reliance upon such facts which has led
to the concrescence theory of tooth development now so rife
in Germany, and which seems so absurd when viewed in the
light of palaeontology.

I have no intention of belittling the splendid services which
embryology has rendered to morphology, but merely to point
out that this method alone cannot reach finality any better
than comparative anatomy. It resembles dealing with a lit-
erature that has been vitiated by many forgeries, only the
grossest and most palpable of which can be readily detected.

A third method of attacking morphological problems is that
offered by palaeontology. Let us begin our consideration of
this method by frankly acknowledging its drawbacks and limita-
tions, (i) In the first place there is the imperfection of the
geological record. Palaeontology does not profess and never
can hope to reconstruct the whole history of life upon the
earth, or even the greater part of that history ; very many
chapters are irretrievably lost, and others are so fragmentary
that they teach us little or nothing. The great sedimentary
deposits which contain nearly the whole recorded history of
the globe were laid down under water, and for a land animal

PALAEONTOLOGY AS A DISCIPLINE. 49

or plant to be entombed there is a lucky accident. If all we
could learn of the terrestrial life of North America had to be
deciphered from the fragments enclosed in the oceanic deposits
along its shores, how very imperfect would our knowledge be !
Although the estuarine, swamp, and lake formations, which
occur on such a grand scale among the rocks of the earth's
crust, have preserved whole chapters in the history of terrestrial
life with wonderful fullness and accuracy, they are all too few
and too widely separated to form any complete record. Even
in a continuous series of marine deposits, representing vast
periods of time, there are sure to be gaps of greater or less
importance in the record. Changes in the depth of water and
the character of the bottom will drive out one set of forms
from that locality and bring in another, which has no genetic
connection with the former, which may perhaps return with a
renewal of the old conditions. Many groups of organisms are
incapable of preservation in the fossil state, except under the
rarest conditions — conditions which occur so seldom and so
widely separated in space and time, as to render hopeless any
attempt to reconstruct a continuous story from them.

The very circumstances under which organisms are preserved
in the rocks offer another obstacle to the determination of
phyletic series. On examining large collections of fossils from
several successive horizons, we find that the majority of the
species and even of the genera are confined to one or two for-
mations, and that each succeeding fauna is recruited partly by
migrations from other regions and partly by the rapid expansion
of comparatively few adaptive and plastic types, while most of
the forms which were especially well fitted for the older con-
ditions die out under the new. The collections are, of course,
largely made up from the abundant and dominant species of
each horizon, which frequently are not the ancestors of those
which will be dominant in the succeeding one. The sudden
appearance, as it so often seems to be, of a fully differentiated
group is sometimes due to that cause, sometimes to a migration
from some other region. Even in phyletic series which are
well-nigh complete, there is a tendency for each successive
genus to undergo similar cycles of specific variation and this

50 BIOLOGICAL LECTURES.

adds to the confusion, the very completeness of the record
increasing the difficulty of its interpretation.

(2) A second drawback to the palaeontological method of
inquiry lies in the incomplete preservation of those organisms
which are fossilized. Of plants we find, for the most part,
only scattered leaves, rarely the reproductive organs, stems, or
roots, and often the proper association of the various parts
requires the strenuous labor of years. Of animals, except
under exceedingly rare circumstances, only the hard parts,
teeth, bones, shells, and the like, are preserved, and in the case
of vertebrates how seldom is even the skeleton completely
recovered ! As in plants, the association of the various parts
of a single skeleton may require the long-continued and
laborious efforts of many workers. Extraordinary blunders
have sometimes been committed in this work. In the remark-
able genus Chalicotheriiim the skull was at first referred to one
mammalian order and the feet to another, and Forsyth-Major's
suggestion that they all belonged together was received with
incredulity. Of the even more curious Agriochcenis the head
was ascribed to one order, the fore-leg to a second, and the
hind-foot to a third.

The utterly false notion, which nothing seems able to eradi-
cate, that the palaeontologist can readily restore an extinct
type from a single bone or tooth, ought to receive its quietus
from such examples, though of course it will not. It is
equivalent to saying that we have nothing to learn from the
fossils, and that all possible types of structure are exemplified
in the living world.

On account of this incompleteness of preservation we cannot
learn much that we wish to know of the structure of extinct
organisms. The nervous, vascular, muscular, and alimentary
systems are entirely lost and can be inferred only from indirect
and often insufficient evidence. Were the pearly nautilus
extinct, our notions of the anatomy of the tetrabranchiate
cephalopods would be very much astray, and in the cases of
several groups of fossils we are quite unable to interpret the
structure from what remains.

(3) A third difficulty in the way of a truly morphological

PALAEONTOLOGY AS A DISCIPLINE.

51

palaeontology consists in the uncertainties of geological cor-
relation, by which the relative age of formations in widely
separated areas and different continents is to be determined.
It may and often does make a vital difference in the construc-
tion of a phylogeny, whether a given set of rocks in North
America is older or younger than one in Europe, with which it
is correlated. The principles according to which such corre-
lation is to be made are still somewhat indeterminate, and not
a few geologists maintain that the problem is an insoluble one.
On the other hand, it is essential to the palaeontologist that it
should be solved, and already a very encouraging beginning
has been made.

(4) In the fourth place the apparent order of succession of
organisms in the stratified rocks must not be too implicitly
and uncritically accepted. Animals and plants diffuse them-
selves as widely as possible until stopped by some impassable
barrier. During the long ages of the world's history these
migrations have ever been in progress, and they greatly confuse
the record when we attempt to read it in terms of evolutionary
descent. A species in a newer formation, which appears to be
derived from one in an older horizon of the same region, may,
as a matter of fact, have had an entirely different ancestry and
have migrated half around the globe to the place where it
occurs. To make these distinctions theoretically is easy, to
apply them very difficult.

(5) Lastly should be mentioned a practical drawback to the
palaeontological method, namely, its costliness. The naturalist
may find much to do in other departments at small expense,
which will be a source of infinite pleasure to himself and of
great value to science. Every field and wood, every pond and
stream, and above all the sea, offer boundless stores of ma-
terial. Even the side of palaeontology which bears upon
stratigraphy and historical geology may be taken up to
great advantage by the private worker who happens to live
in a favorable locality. With palaeontology as a branch of
morphology, however, the case is unhappily very different.
Here great collections brought together without much regard
to cost, skilled workers to prepare the specimens, and great

52 BIOLOGICAL LECTURES.

buildings in which to house them are indispensable. Distant
regions must be examined and the whole world ransacked for
material. Many problems connected with the North Ameri-
can fauna must await their explanation until Asia can be
thoroughly explored, while Africa and South America have
already shown what a complete geological knowledge of those
continents may be expected to teach. • In this country the
arid parts of the West have yielded a marvelous store of
wonderfully preserved fossils, but great sums have been
expended in gathering them, — an opportunity which falls to the
lot of but few. It is to be hoped that the multiplication of
museums may ere long put within the reach of all biological
students something of these marvelous stores of wealth.

It might well seem that all these limitations and drawbacks
would necessarily disqualify palaeontology as a morphological
subject from being of the smallest real importance, but such a
conclusion would be highly erroneous. Several of the limita-
tions are but partial, not applying to particular cases, while
others are difficulties that further investigation may hope to
remove, not insurmountable obstacles. Every year new forms
are discovered and better material of known forms. Though
the White River Bad Lands have for more than half a century
been classic collecting ground, hardly a season passes that
several new genera are not registered from there, and, better
still, types before known only from fragments are gradually
made more and more complete. From the middle Eocene to
the lower Miocene there is in the West an almost unbroken
transition which is bringing forth a truly magnificent series of
evolutionary stages.

While palaeontology, as we have seen, does not profess to
give an unbroken life-history of the earth, yet it has certain
preeminent advantages which neither comparative anatomy nor
embryology possesses, and which fit it to form an invaluable
supplement to those other methods of morphological investiga-
tion.

(i) In the first place, it gives us in many cases actual
phyletic series in their true order of succession in time. In
many groups of animals we have already recovered phyletic

PALEONTOLOGY AS A DISCIPLLWE.

53

series so full, so complete, that no observer can hesitate to
accept them as representing actually or very nearly the succes-
sive steps of evolutionary change in the order in which they
occurred. Little confidence may, perhaps, be placed in these
phyla by those who have not made a special study of them,
and it may be imagined that fuller knowledge will require
them to be completely changed. But when we find such a
series as that of the horses, leading back by almost imper-
ceptible gradations from the great monodactyl living forms to
their little five-toed progenitors in the far distant Eocene
times, doubt becomes well-nigh impossible. A limit of error
is placed by the stratigraphical order, the geological and
morphological successions coinciding beautifully. Whatever
changes in the details of such a series, a radical reconstruction
of it is not in the least likely to be called for. Few observers,
if any, would now uphold the arrangement of the equine
phylum proposed by Kowalevsky, namely, Palceotkeriiim,
Anchitherhinty Hipparion, Eqtms ; and yet it is surprising
to see how the general character of this series and the deduc-
tions as to the manner of evolution which may be drawn from
it agree with those made on the basis of the equine series as
we now have it. Kowalevsky's mistake merely consisted in
putting certain members of the side branches into the main
line of descent, and that similar errors have been made in
accepted phylogenies is not at all unlikely. The correction of
such errors will, however, change the general result but little,
and we may appeal with considerable confidence to the con-
clusion which legitimately follows from a study of these
phylogenies.

Fortunately, the well-defined phyletic series which have
already been made out occur in very widely separated animal
groups, — mammals, reptiles, cephalopods, brachiopods, echino-
derms, etc., — so that the points in which they agree are apt to
prove of general application and validity. The cephalopods
are particularly valuable in this connection, because in them
the embryonic and young stages of the shell are preserved in
the adult, and thus conclusions have a distinct support from
embryological considerations. To recur to the linguistic

54 BIOLOGICAL LECTURES.

analogy, we have here at least fragments, and sometimes very
extensive ones, of the various literatures which register the
changes of language, and in the original documents which bear
evidence of their dates and succession, and which, however
incomplete, have not been falsified by forgeries and late inter-
polations. In this way we may establish unequivocally some,
at least, of the animal pedigrees, which it is one of the great
objects of morphology to construct, and thus to correct the
results obtained by the other methods of inquiry. Palaeon-
tology further enables us accurately to discriminate between
resemblances which are due to genetic affinity and those which
result from parallelism or convergence.

To illustrate : On grounds of comparative anatomy Flower
classified the land Carnivora into three sections : the Cynoidea,
or dogs ; the Arctoidea, containing the bears, raccoons, and
mustelines ; and the Aeluroidea, including the civets, hyenas,
and cats. This classification has found wide favor and very
general acceptance, but palaeontology shows it to be untenable.
The extinct phyla show that the dogs and bears are very closely
akin, as are the mustelines, civets, and hyenas, while the cats
occupy a very isolated position, and are not closely allied to
any of the other families. The anatomical characters which
suggested Flower's system are in part examples of conver-
gence and in part due to the retention of primitive characters
in some groups and their loss in others.

Again, reasoning from embryological data. Rose and others
have propounded the theory that the complex, multicuspidate,
mammalian tooth has been formed by the coalescence of many
simple teeth. The phyletic series enable us to follow the
evolution of these teeth step by step, and demonstrate the
incorrectness of the ''concrescence theory." In fact, the
great lesson which the study of the phyla continually brings
home to the observer is, that trustworthy results are to be
obtained only by the laborious and minute tracing of the
changes through every step of the way. Fragmentary series
are not to be depended upon, and the wider the gaps between
their members the more uncertain is their connection.

(2) The reconstruction of pedigrees, the solving of homol-

paljEontology as a discipline. 55

ogies, the determination of relationships, and the estabhshing
of classification upon a sound and natural basis, important as
these are, are yet only a part of the great task which mor-
phology has set before itself. We wish to penetrate more
deeply into the mystery of nature, and learn how and why
these changes have occurred ; or, in other words, to discover
the manner in which, and the efficient causes by which, devel-
opment is effected. On these subjects there is, as yet, wide
divergence of view among morphologists. The postulates and
assumptions upon which morphological discussions are founded
are, in great measure, incapable of proof, and appeal with very
different degrees of force to different minds. Modes of devel-
opment which appear axiomatic to one observer are by another
regarded as absurd. All are agreed that there are limits to the
possibilities of change ; no one attempts to derive a butterfly
from a beetle, or a horse from a cow; but just how and where
these limits should be drawn it is at present impossible to say.
It is this uncertainty which refers the question to the individual
judgment, and leaves the way open for such radical differences
of opinion.

To the solution of these problems of evolutionary modes
palaeontology offers most valuable assistance, drawn from the
study of actual phyla. It might seem that this was merely
arguing in a circle, because the construction of phylogenetic
series involves certain presuppositions as to what changes
are and what are not possible, and we then proceed to prove
the presuppositions by the phyla thus constructed. But the
cautious, step-by-step method, guarded by the order of appear-
ance in time, offers a way of escape, and enables us to con-
struct phyla in harmonious structural and stratigraphical
succession, which must very nearly represent the actual stages
of change. Only a beginning has been made in this work, but
the results drawn from an examination of widely separated
phyla, such as mammals, gasteropods, and cephalopods, are so
consistent and harmonious as to be full of promise for the
future.

Limitations of time and space forbid an attempt to fully
consider here all the deductions which have been suggested

56 BIOLOGICAL LECTURES.

and rendered more or less probable by this method, but one or
two principles which stand out with especial clearness may be
mentioned.

{a) Evolution is ordinarily a continuous process of change
by means of small gradations. The continuous character of a
phylum is apt to be proportional to the relative abundance of
its representatives in the strata, which is equivalent to saying
that well-known series are continuous, while apparently dis-
continuous series are imperfectly known. This does not imply
that the rate of change was always uniform, — it probably was
not, — or that a sudden alteration of conditions may not bring
about discontinuity, or per saltum development. It means
that the usual and normal mode of advance is by continuity
of change.

ib) Development is, in most instances, direct and unswerv-
ing. The rise of new forms, and the decadence and degen-
eration of old ones, are not ordinarily by zigzag and meandering
paths, but by relatively straight ones ; and though, of course,
a path once taken may be diverged from, yet in such a case it
is not regained. This applies particularly to the organism as
a whole ; in minor details more latitude is permissible. The
evidence is not yet sufficient to show just how widely applicable
this principle is.

{c) Parallelism and convergence of development are much
more general and important modes of evolution than is com-
monly supposed. By parallelism is meant the independent
acquisition of similar structure in forms which are themselves
nearly related, and by convergence such acquisition in forms
which are not closely related, and thus in one or more respects
come to be more nearly alike than were their ancestors.
While some observers have tacitly or explicitly denied the
reality of these processes, most authorities have been com-
pelled to admit them. What palaeontology has done, and is
doing, is to show the universality of these modes of develop-
ment, and to point them out in directions where they had not
been suspected. To give a few examples. The crescentic, or
selenodont molar, has been separately acquired by no less than
three groups of artiodactyls, and probably others as well. The

PALAEONTOLOGY AS A DISCIPLINE. 57

spout-shaped odontoid process of the axis has independently
developed in the horses, the tapirs, and in three artiodactyl
series. The true ruminants (Pecora) of the present day are,
among other characteristics, distinguished from the remaining
artiodactyls by the hollow tympanic bullae, which in the pigs,
tragulines, and camels are filled with cancelli, or spongy bone.
In Oligocene times only the camels had acquired the cancelli ;
the other groups, though already differentiated as such, still
had hollow and inflated tympanies. Lists of such parallelisms
in single characters might be multiplied almost indefinitely,
but they also occur in whole groups of structures. The
camels have in teeth, skull, vertebrae, and limbs many points
of resemblance to the true ruminants, which demonstrably are
not due to inheritance from a common ancestor. The two
great series of ungulates, the artiodactyls and perissodactyls,
which are usually grouped together as the Ungulata par excel-
lence, are examples of parallel development on a grand scale,
their many resemblances being, for the most part, independ-
ently acquired. The flesh-eaters known as Carnivora include
at least two, and probably three lines, which have been sep-
arately given off from the primitive flesh-eaters, or creodonts.

Such a mode of development greatly increases the difficulty
of determining phylogenies, which would be very much easier
could every notable resemblance at once be accepted as proof
of relationship. It often renders impossible the proper classi-
fication of some isolated genus which seems to have several
incompatible affinities. It emphasizes the necessity of found-
ing schemes of classification upon the totality of structure, and
of determining the value of characteristics, whether they are
primitive or acquired, divergent, parallel, or convergent, before
attempting to assign them their proper taxonomic value.

We may find a practical identity in teeth, skull, or feet as
the outcome of these processes, but as yet no case is known
where all these structures have become alike through the opera-
tion of either parallel or convergent development. Among the
invertebrates the case is different. Hyatt has shown that the
degenerate, straight-shelled, ammonoid genus Baculites is a
polyphyletic group, and derived from several distinct stocks,

58 BIOLOGICAL LECTURES.

both European and American. Wiirtenberger points out that
the so-called Ammonites mutabilis is not a true species, but a
composite group, made up by the convergence of several dis-
tinct lines to a common. This case is peculiarly significant,
because it would hardly have been detected had not the
embryonic and young stages of the shells been preserved.

It seems the most obvious of commonplaces to say that
numerous and close resemblances of structure are prima facie
evidences of relationship. Yet the statement is true, even
though the resemblances have been independently acquired,
because parallelism is a more frequently observed phenomenon
than convergence, and because the more nearly related any
two organisms are, the more likely are they to undergo similar
modifications.

All this brings us back to the thesis so frequently insisted
upon already, that the only safe and trustworthy method of
constructing phylogenies is by tracing the development, step
by step, through all its gradations ; and until this is done the
classification of any group can be but tentative and provisional,
that is, if we intend classification to express relationship.

No department of biological science is at present the scene
of such vigorous controversy as that which deals with the
factors of evolution, the causes which determine the develop-
ment of new forms, and the problems of heredity which are
inseparably connected with them. Palaeontological evidence
will prove to be of much importance in this connection also,
but it cannot well have more than a corroborative value.
Though the examination of long and complete phyla brings to
light much that is suggestive concerning the factors which
have brought these changes to pass, and any rational theory
must embrace and explain these facts, yet the deciding weight
must probably come through the physiological and experi-
mental method. Time fails to deal with such far-reaching
questions here, and yet it may be well to call attention to the
necessity of avoiding a dogmatic and intolerant attitude, and
to deprecate any premature attempt to exclude this or that
class of factors from consideration. In most of the recent
writings upon the efficient causes of evolution you will find

PALEONTOLOGY AS A DISCIPLINE. 59

expressed or implied the feeling that these matters are not
so simple and intelligible as we once supposed, and that
we are yet only upon the threshold of its solution. The
study of palaeontology will not tend to dispel this feeling of
mystery.

Another department of biological science in which palaeon-
tology has proved of great value, and will become more and
more so in the future, is that which deals with the geograph-
ical distribution and migrations of organisms. Though not a
branch of morphology, this subject has a very significant
bearing upon that science, and cannot be ignored in any com-
prehensive theory of evolution. This, again, is too large a
field to enter upon at the close of a lecture. It must suffice,
therefore, to hint at the many cases in the existing distribu-
tion of animals, which seem so puzzling and capricious, and
which are so readily explained by a study of the past. That
the nearest allies of the South American llamas should be the
camels of the Old World seems unaccountable until we learn
that North America was the original home of the entire tribe.
The occurrence of the tapirs in South America and in the
Malay Peninsula becomes intelligible enough when we learn
that this genus is of very high antiquity, and was formerly
represented in every part of the northern hemisphere.

The more fully the past is recovered the more completely
the former land connections of the various continents are made
out, the more comprehensible do the seeming anomalies of the
present order of things become, — a proposition which applies
to more than problems of geographical distribution.

The foregoing consideration of palaeontology as a branch of
morphological science is necessarily brief and very inadequate,
but it will suffice, I trust, to show that its claims upon the
attention of morphologists should not be ignored, and that it
is admirably fitted to throw light upon many obscure problems.
In conclusion, let me point out that final and lasting results
are not to be gained by an exclusive adherence to any method
of morphological inquiry, but by a combination of all of them.
Each is able to supplement the others, and it is folly to reject
such aid. Already most encouraging results have followed

6o BIOLOGICAL LECTURES,

from this combined method of work, and it is devoutly to be
wished that its scope may be more and more extended. As an
example may be cited the recent investigations upon the
mammalian dentition. From palaeontological phyla we have
learned to distinguish the homologies of the cusps, and the
way in which a complex tooth is gradually formed from a
simple one. Embryology, on the other hand, has shown the
relations of the successive dentitions to one another in a
fashion that palaeontology could by no possibility accomplish
unaided. As another example may be mentioned Wincza's
discovery of a bony clavicle in the embryo of the sheep, which
was soon followed by the still more unexpected one of vestigial
bony clavicles in certain extinct artiodactyls, confirming and
explaining the first. Embryology has taught us that the large
element in the carpus of the Carnivora known as the scapho-
lunar was formed by the coalescence of three separate bones,
— the scaphoid, lunar, and centrale. Later the fossils were
unearthed, which showed that the embryonic and transitory
condition of the modern forms was the permanent and adult
structure of the primitive Eocene flesh-eaters.

The more the combined method is employed the more
fruitful does it appear. Nor should the combination be
restricted to the technically morphological subjects. Experi-
mental embryology has already won some notable triumphs,
and that is a physiological quite as much as a morphological
province.

In the ever-increasing complexity of modern civilization a
more and more important r61e is played by systematic coopera-
tion, specialists combining for joint work which neither could
accomplish alone. Is it Utopian to wish that some such
organized scheme of attack upon biological problems shall
be devised, when, instead of every man doing merely that
which is right in his own eyes, we shall combine in a definite,
orderly way to investigate a given topic in all its bearings } It
may well be doubted whether any naturalist, however great his
genius, will ever again be able to take such an exhaustive
survey of biological data as Darwin did in his time. The
enormous mass of accumulated facts already far transcends

PALEONTOLOGY AS A DISCIPLINE. 6 1

the power of any one mind to grasp, and it would seem that
organized cooperation is the only method of dealing with such
vast accumulations. When that time arrives the palaeontolo-
gist will be able to render even more conspicuously valuable
services than he has done in the past.

FIFTH LECTURE.

EXPLANATIONS, OR HOW PHENOMENA ARE
INTERPRETED.

BY A. E. DOLBEAR.
(Tufts College, College Hill, Mass.)

How long a time mankind has been on the earth no one
knows. When I was a lad I was taught that the earth was
made about six thousand years ago. Archbishop Usher's
chronology was accepted by all except a few geologists, and
their conclusions were considered as speculative vagaries, in-
vented by men whose object was to bring the Bible into dis-
repute, and against whom it was the duty of men who loved
the truth and who believed they possessed it to warn the young.
Now it is believed that the great pyramid of Gizeh has been
standing for nearly, if not quite as long a time, and Egypt was
a thickly settled country with well-established government,
laws, customs, religion which had then existed for a long time.
Back of Egypt was Assyria and other peoples, and farther back
still other peoples, and so on till all was lost in an antiquity
reaching back probably fifty thousand years and perhaps twice
that period. What has brought about the change in opinion
as to a matter of that character which cannot be rigorously
demonstrated, and why has any one more than a speculative
interest in it ? The answer to the first is that new data have
been found bearing upon the question which our ancestors did
not have, and a necessity was felt for making every kind of testi-
mony logically consistent with every other kind. To the
second, one must say that every thoughtful person who is
interested in his own existence and humanity has hopes and
fears ; he is aware without reasoning upon it that a knowledge

64 BIOLOGICAL LECTURES,

of the past must help to a knowledge of the future, and if he
can properly interpret the past of mankind he will the better
know what to anticipate for them and himself. So long as
creation was supposed to be by fiat and the universe to have
sprung into existence just as Minerva was said to have sprung
from the brain of Jupiter, there was no trouble. Everything
was satisfactorily explained by saying God did it. The ques-
tion how did not concern any one, for miracle was the method
of deity, and needed no antecedent but the will of the deity.
All effort was given to establishing the authenticity of the
biblical record. It was held to be such an important matter
that no one was allowed to question it, or assume even for an
instant that it was not the exact truth. The importance of a
knowledge of the past history of mankind is as great as ever ;
its interest has not abated but increased. The origin and
destiny of mankind are still the primal questions, and all knowl-
edge in any department of human effort has its main reason
for the light it may throw on these.

In this, as in most other works, there are two ways which
men have adopted to satisfy their philosophical wants. One
is to assume what is thought to be an adequate fundamental
cause or principle, a mode of operation, and a certain logical
process also believed to be reliable, and with these to construct by
a deductive process the observed phenomena. For instance, to
account for, say, the Solar system as it appears to-day. Such
a philosopher would assume first, the existence of a deity with
the attributes of omniscience, omnipotence and will, existing
and related to time and space as we are. Secondly, he assumes
that the mode of operation was radically different from any he
knows of or can imagine, namely, the creation of both matter
with all its qualities and also energy as we know it, for we
know of energy only as existing in something already formed.
And thirdly, he assumes with these that he may trust his logi-
cal process and reach the conclusion that the existence of the
Solar system and everything happening in it is properly ex-
plained by assumptions, neither of which are in accordance
with human experience. For first, has not the proof, absolute
proof, of the existence of God been the attempt and the despair

HOIV PHENOMENA ARE INTERPRETED. 65

of philosophers ? If we possess it to-day in the sense that
we possess proof, — say, of the North Pole or the existence of
the ether of space, — where is it to be found ? Proof of the
latter compels assent as soon as perceived, yet every one feels
there is something desirable lacking in the former. It may be
more or less probable, but certainty is what we are talking
about.

Again, creation implies a process by which nothing becomes
something. If the matter which constitutes the world was
simply formed out of something else which was not matter,
then it is that something else we are concerned about, and the
inquiry properly belongs to that antecedent something. Now
all of our experiences in any field are with matter and with
forms of energy. Experience with the former has led to the
conviction that its quantity is not changed in the slightest
degree by any kind of a physical or chemical process. Once it
was thought possible to change lead to gold, but it was in the
prescientific age when chemical products were not weighed in
the balance, and the spectra of the elements had not been seen.
Experience with energy has led to the formulation embodied
in the doctrine of the Conservation of Energy, namely, that
the quantity of energy in the universe is constant. No kind
of changes alters the quantity. If these deductions from expe-
rience be true, it follows that either what we call matter and
energy have always existed, or, if either had a beginning, it
must have been by some process out of all relation to every-
thing we know, — one which can neither be described nor
imagined, and explanation is therefore impossible, if explana-
tion means what we mean by it when applied to such a process
as, say, the generation of electricity in a dynamo ; for in
this we have definite known antecedents of steam power, heat,
and so on. In experience we have only transformations, all
of which imply matter as the condition of transformations.
The creation of energy is a radically different affair, and it
is a fair question, by what warrant does any one assume a
process wholly foreign to experience as a basis of a philos-
ophy of experience ?

Again, the fallibility of human logic has been so many times

66 BIOLOGICAL LECTURES.

shown, and in so many different fields when applied in cases
where verification has been possible, that one may well hesitate
about holding very fast to any conclusion which has not yet
been adjudicated by experience. This holds as true for what
we call philosophy as for science. We are in possession of a
body of scientific doctrines or propositions about material
phenomena which are satisfactory to this extent : they have
met all the criticism to which they have been subject by men
of every nation who have concerned themselves with them.
Such, for instance, are the doctrines of mathematics, of astron-
omy, of geology, and some others in physical science, all of
which deal with verifiable matters, that is, with matter and the
forms of energy and their relations. In gaining this degree of
certainty there has been a series of steps taken tentatively,
engrossing the attention of men interested in science for a
century or two. The thing to note here is, that obvious as
many of these propositions are to us, now they are pointed out,
they were so far from obvious to our predecessors that almost
every other conjecture was entertained, and often with no
attempt at verification before the present ones were adopted.
This is of so much importance that some examples may be use-
ful to make plain the meaning. Take the case of the explana-
tion of the position and motions of the earth, and other bodies.
First, as to the center of creation about which sun, moon, and
stars revolved. The apparent was taken to be the truth, and
the difficulties of such an explanation of the apparent were
quite ignored, and the necessity of having some sort of an
answer to the question as to the causes of day and night was
so great that such an explanation was thought to be better
than nothing. After that came Ptolemy's explanation, a w^on-
derful and intricate system of cycles and epicycles which
mechanically would not work, but served for a time better than
the one it displaced. Then came Copernicus with the plan of
the sun as the center with the planets and the earth revolving
about it. This simplified the problem, but the reason given
for supposing the orbits of the earth and the planets to be
circular was not a physical reason, — that is, not an observed
or calculated one, but a metaphysical reason ; that is, one

HOW PHENOMENA ARE INTERPRETED. 67

which was imagined to be in accordance with moral quality.
The Almighty had made things perfect ; a circle was the only
perfect circuit. Kepler discovered that none of the bodies
involved moved in circles but in ellipses, and this is known as
one of Kepler's laws. But Kepler, unable to imagine how
such bodies could move in such ellipses as he observed they
did, and, like others, feeling obliged to give some sort of an
explanation for the apparent anomaly, invented guiding spirits
whose office was to thus move the heavenly bodies. Then
came Sir Isaac Newton, who showed that, with gravitation
assumed, all the observed motions were accounted for, and
further, that the so-called perfect circle orbit was the only
unstable orbit.

In this series of steps towards the explanation of observed
phenomena, the first was wrong in every particular. The
others were wrong, and wholly wrong, to just the extent they
departed from simple mechanical relations and incorporated
unmechanical and unrelated notions with their explanations.
Again, it has been thought a reasonable explanation of the
relations and motions of the bodies which make up the Solar
system that they were thus created, each one at its proper dis-
tance from the sun, and with rotations and revolutions properly
adjusted for stability. The Solar system started thus. No
reason or explanation was needed save that it was the will of
an omnipotent creator which, as already pointed out, is not an
explanation but a reference to the unexplainable. Kant per-
ceived that the involved relations were probably of a mathe-
matical sort, and inferred there was probably some simple
mechanical explanation of the whole arrangement. Laplace
attacked the problem and showed if the material which now
makes up the Solar system had been scattered in space in a
gaseous form, gravitation would bring it to just such a system
of globes, with masses, distances, rates of rotation and satellites
as we find them to have. The telescopes at that time showed
many patches of nebulous masses in the sky ; but as the tele-
scope was improved many of these patches were seen to be
dense clusters of stars, and the inference was fairly allowable
that with sufficient telescopic power all might in a similar way

68 BIOLOGICAL LECTURES.

be resolved. The spectroscope, an instrument for determining
whether matter is solid or gaseous, when turned towards the
sky showed that there were vast numbers of gaseous masses
there and in many degrees of condensation. This discovery
was held to corroborate the idea of Kant and Laplace, so that
to-day there is no astronomer who does not hold the view that
the Solar system as we see it to-day is a growth, that it was
not made as it is, and that gravity with the simple laws of
motion are sufficient in themselves to organize the Solar
system as we find it, and an explanation of it is an exposition
of how these factors brought it about.

The distribution of land and water, mountains, valleys, rocks
and their contents in like manner were held to be explained by
the statement that they were thus created substantially as we
find them. When it was noted that animal and vegetable
remains were to be found in abundance in many rocks, very
little thought was needed to induce the question : If these
rocks have been in place from the beginning, how came they
to be filled with evidences of marine life such as fossils attest }
Did the ocean once cover the mountain tops } Once the
attempt was made to explain their presence by reference to
Noah's flood which was held to have covered mountain tops,
but the fossils were to be found through great rock formations
and through rock depths of miles. It was noticed presently
that the lower formations had simpler forms and the lowest
rocks none at all. There was but one meaning to all this,
namely, the surface of the earth had been depressed and
elevated above their present level, that the ocean must have
once covered what is now a mountain chain. It was also noted
that slow changes in elevation are now going on in many places.
The coast of France is sinking, the coast of Norway rising.
The temple of Jupiter Serapis has twice been submerged in
the Mediterranean Sea and is now out of water. The Missis-
sippi River is building shores in the Gulf of Mexico at the rate
of a mile or two a year with the detritus brought from the
central valleys of the United States, and Niagara Falls is
retreating at the rate of a foot or two a year. Such phenomena
imply unstable land and water surfaces. The physical features

HOIV PHENOMENA ARE INTERPRETED. 69

of the earth are changing slowly. In time they can change
to an unlimited extent. Geologists explain all geologic phe-
nomena as due to physical causes such as are now going on ;
but the implication is that, given simply time, everything
we observe of this character is easily understood, — with no
appeal to other than such factors as are at work before our
eyes, — and, with such a background as is afforded by an appeal
to astronomy, there is good reason for holding that no other
physical factors than the ordinary type have been involved in
the geologic phenomena. Geological facts are explained by
presenting their physical antecedents, and the explanation stops
when traced to these, that is to say, when in the territory of
astronomy or physics.

Once more : only a generation ago men believed that all
species of animals and plants upon the earth were descended
from similar forms without modification from the original ones
created by fiat. The horse of to-day is like his ancestor of
thousands of years ago, the lily like the original. In like
manner all plants and animals and men represented in form
and qualities their prototypes. Not because any one had ever
been a witness to such a process of creation nor because there
were other evidences which deserved attention, but it was a
kind of habit of mind to pretend to explain phenomena by
referring to some inexplicable process out of all relations with
experience. In 1846 a book was published anonymously, called
Vestiges of Creation. It attempted to show that all the present
forms of life might have resulted from the simplest forms of
life by a series of small, almost insensible changes in the
organisms, if these were continued for a great number of
generations. The idea was condemned by almost everybody
interested in the question, not from defective evidence, but
simply because it required the abandonment of a belief that
had not a particle of evidence in its favor. That is to say, an
attempted explanation which had much experience in its favor
was rejected by theologians and naturalists alike, and another
explanation, having not a particle of evidence and no degree of
probability, was held to. Since the time of Darwin all that
has been changed. The view advocated in Vestiges, though not

JO BIOLOGICAL LECTURES.

with such conclusiveness as by Darwin, has been generally
adopted by naturalists of every nation.

To accept Darwin is to accept the proposition that there
never was a first horse or first rose or first man. The
ancestry of the horse has been traced back through a long
series of forms as far as an extinct animal, known in zoology as
the paleotherium, which was no more like a modern horse than
is a tapir; but this distant animal may have been extinct for a
million years or more. No matter how long now, the point is
that the old notion has been given up, and appeal has been
^made for all changes in form, size, habits, and adaptations to
processes now going on, and all appeal to other or superphysical
agencies has been abandoned by naturalists of every country.
This means that in such important matters as the phenomena
of living things there is felt to be no necessity for going
beyond ordinary factors operating to-day, in precisely the same
sense as was the case of geology and astronomy. The expla-
nations accord with experience, and exposition is only the pre-
senting of factors and conditions in their proper order. The
explanations in each of these are adequate only when the ante-
cedents are sufficiently well known to make it plain they need
no supplementary, unrelated factors.

We hear in these days of the forces of nature, of heat, of
light, of electricity, and the latter especially is popularly con-
sidered as a very mysterious something which nobody can
understand. These factors are supposed to act upon matter
and compel it to do this or that, go here and there. Heat in
the old books was often called caloric, and that was supposed
to be an imponderable something which could now be in matter
and now out. When in it, it caused the matter to exhibit
certain kinds of phenomena; when it was out, none inquired as
to where it was or what it was about. During this century it
has been conclusively proved that heat is but a particular kind
of motion. When one body strikes another body it imparts
some of its motion to it for mechanical reasons, and if a body
possessing heat motion comes in contact with another body
having less of that kind, it imparts some of that heat to it.
What one loses the other gains. There has been nothing

HOW PHENOMENA ARE INTERPRETED. 71

more mysterious than an exchange of motion ; there is no
imponderable substance to be now in and now out, — only a
change in the conditions. Taking this view of heat it is easy
to see that the terminology served to mislead thinking ; but the
view here presented shows that heat cannot be properly
called a force any more than the vibrations of a bell or a piano
string can be called a force, and so heat is out of the category
of force.

Light was also an imponderable substance. Now we know
it to be wave motion in the ether, and the vibrations that con-
stitute the heat of molecules set up these waves in the ether,
and the latter conducts them away at the high rate of 186,000
miles a second. The heat motions are the antecedents of the
light motions in the ether in every case, and every ray of light
when traced back to its source ends in a vibrating molecule.
So if heat be not a force, neither can light be so considered,
and two of the imponderables are gone as forces.

Electricity as another wonderful force is known to originate
in the motions of molecules, for both by chemical action and
by heat action it is produced. It also disappears when allowed
to do either chemical, thermal, or mechanical work. As it has
molecular motion for its antecedent and molecular work for
its resultant, it follows that its nature cannot be materially
different from that of the others. Indeed, so well established
are these interrelations between heat and electricity that large
industrial enterprises are founded upon them. The point here
is that electricity, as an independent something, — a force that
may be summoned like an Afrite in The Arabian Nights to do
duty for a while and then be dismissed from service to be no
one knows where, — is an idea wholly wrong. It is a condition,
not a thing, for electrical energy may be wholly transformed
into heat energy or into light or other kinds of work. So far
we have only matter and forms of motion in matter, and forces
as such have no existence. And if this be true it will be well
to abandon the notion of either of these agencies as forces or
things having an existence apart from matter. There is no
evidence for such a view, and any quantity of evidence against
it. The explanation of the phenomena due to either or all of

72 BIOLOGICAL LECTURES.

them requires nothing beyond the factors I have already named,
and there is no need of assuming anything more mysterious
than these. If all phenomena in the realm of the so-called
inorganic nature be due to matter and its various motions, — and
of this there seems to be little reason to doubt, and no one
argues otherwise, — then what is the use of talking about forces
of any kind, seeing they have no existence. How much differ-
ence this will presently make in one's conceptions any one
may discover by omitting the use of the word ''force " from
his vocabulary for' a day or two, whenever he discourses and at-
tempts an explanation of a phenomenon. It will be perceived
that the word is used generally as a pretentious substitute for
ignorance.

Living things, both plants and animals, were thought for a
long time to be endowed with a quality radically different from
inanimate things. The processes of digestion, assimilation,
growth, and the like were believed to be dependent upon a
peculiar agency capable of dominating the ordinary chemical
activities which otherwise would destroy the organism. This
was called vital force. Organic chemistry was the name given
to the processes by which a host of complex compounds were
formed in living things, and vital force was credited with being
the agency in all of them. By and by a chemist succeeded in
producing in an artificial way a single one of these products,
and the announcement was a stunner to both physiologists and
chemists. Soon other chemists found artificial ways of making
others, and to-day so great a number have been produced in
the laboratory that chemists do not hesitate to express their
belief that every organic substance, even protoplasm, may thus
be formed, and that also in the animal body there is no such
agency at all as was called vital force. Physiologists trace
physiological phenomena without exception to the activities of
ordinary forms of energy known as physical and chemical, not
because chemists have been able to build up all compounds
known, but because among the tens of thousands which have
been thus formed there is nothing more required than what
can be provided in a test tube ; and also because it has been
fairly well proved that there is a direct and quantitative rela-

HOIV PHENOMENA ARE INTERPRETED. 73

tion between the energy of food and bodily activity of every
kind ; that no more comes out of the bodily machine in the
shape of work, physical or mental, than is physically provided
by the foods digested. So vital force as an agency in living
things is as mythical as the other forces I have described as
non-existent. An explanation, then, of the phenomena of life
as manifested in either plant or animal is complete when the
physical and chemical antecedents have been presented in
their order and quantitative relations. There appears to be no
reason for holding to the view that there is anything more
mysterious or different in kind in so-called vital phenomena
than there is in what goes on in a test tube in a physical
laboratory. There may be a difference in complexity, not in
agencies.

Of course everybody knows of what is called the conserva-
tion of energy which implies, as I have said already, that the
quantity of energy in the universe is constant, and when any
given kind appears, it is always at the expense of some other
kind which has disappeared, and the two are equal. If the
quantity of matter is not variable, — and that is precisely what
all experience affirms, — and if the quantity of energy is also not
variable, though its forms may be, then the apparent logic of
the case is that one of the factors of energy must be the
variable, and in fact energy as we know it is always a product.
It does not exist as an entity. One cannot assume that the
energy of a moving rifle bullet can be detached from it, so
as to enable one to hold the bullet in one hand and the energy
in the other. The variable factor is simply the rate of motion
the bullet may have, and this rate of motion, whatever it may
be in a given case, had its antecedent in some other body which
lost the motion which was imparted to the bullet. If this be
applied in every case, then it seems that every kind of phenom-
enon involving physical energy — and every phenomenon does
involve such energy — must be due to changes in the kind and
direction and amount of motions a body may have ; and there is
no reason for imagining or supposing in any given case the
existence or activity of any agency differing from or related
to those forms of energy which are investigated in physical

74 BIOLOGICAL LECTURES.

science. Forces dethroned, and matter indestructible, — that is
the result of the scientific activity of the past half century.

When one contemplates that proposition, and thinks of the
wonderful variety of phenomena in the earth and in the
heavens, and then attempts to realize even in a faint way how
all this can possibly come about through the sole agency of
motions of any kind, however complex in their combinations, he
cannot but feel there must somehow and somewhere be an
undetected slip in the logic, or there must be a factor, and a
most important factor, left out ; for at some time in the history
of things, at any rate on the earth, there have appeared not only
living things as plants and animals, but activities of another
class, feelings and intelligence. Along with physical happen-
ings and physical things there has come the senses and the
intellect, the possibility of pleasure, the consciousness and
delight in existence, hopes and fears, and other phenomena,
which cannot by any jugglery of idea or language be resolved
into molecular vibrations or rotations, or any other motions
whatever. They are the things we live for, and care to live
for. These qualities we find in experience to be always associ-
ated with matter and various forms of energy; but the character
of the two classes of phenomena appears so different as to have
led philosophers to the conclusion that they could exist apart,
having no necessary relation to each other ; indeed, the terms
" matter " and " mind " are generally set against each other as
contrasting things which have nothing in common. Matter
has been called dead, inert, and incapable of doing anything
except when other agencies as forces have acted upon it, while
mind has been believed to be the source of life and endowed
with inherent energy. What is energy } The books do not
make it clear. To say it is ability to do work is not to define
it, but to tell what it can do. Wind, water, steam, electricity,
a horse may do work, but no one of them is energy; and energy
is not known in experience when disembodied, that is, outside
of some substantial thing, and then only shows itself in the
degree and kind of activity of that thing. It is in all of our
experiences an exchangeable commodity, but there is never an
exchange except a mass of matter of some degree of magnitude

HO IV PHENOMENA ARE INTERPRETED. 75

is present, and conditions the exchange either in character or
amount. There is no physical thing which possesses it and is
able to impart any of it to another thing without an equal loss
to itself. Yet the above conception of something with inher-
ent energy, able to move other bodies in this way or that, with-
out being depleted in its store, implies as much. To make the
matter clearer, suppose a mechanical engine to be thus endowed
with energy inherent in it and able to act without loss ; evidently
it would be what we would call a perpetual motion, — would give
power indefinitely, and that without any supply for its expendi-
ture. It would mean an infinite source in a finite thing, and a
finite thing which can do an infinite amount of work. If this
be considered as an attribute of mind, that is, such a mind as
humanity exhibits and which each individual of us is assumed
to possess, then each one of us would so far be independent of
antecedents, and would need no other resources, which is con-
trary to our uniform experiences. It should be noted that this
cannot be considered as a matter of degree, that is, ability
to do more or less, for the smallest thing or object possessing
ability to do work of any kind without a physical supply from
some other source can do an infinite amount of work in an
infinite time. The whole has to be granted or nothing. If we
are to eschew romancing and interpret phenomena in accordance
with our uniform experiences, that is, scientifically, — for that is
scientific method, — then it seems plain that one must surrender
the notion that life and mind energize ordinary matter which is
otherwise inert or dead. There is something wrong in one
assumption or the other as to the nature of mind or the nature
of matter or possibly both.

What reason has been given or can be given for supposing
that matter, as we know it, is inert and incapable of doing any-
thing } There are two answers to this, one coming from relig-
ious or theological sources, the other from a physical source ;
the former probably derived from the story of the creation of
living things wherein special creative acts were needed to endow
matter with life, and a second creative effort to endow a living
thing, man, with a soul. Such a view assumed that matter
had in it neither life nor mind, and therefore considered it as

76 BIOLOGICAL LECTURES.

both inert and inanimate. Each particle was imagined to be a
minute something created out of nothing. Its properties were
not inherent in it, but were imposed upon it, and might have
been different if the deity had so willed. Of the latter it is to
be said at the outset that physical philosophers have almost
always accepted their first principles from theologians and have
aimed to the best of their ability to interpret phenomena in
accordance with such assumptions. It was so in astronomy,
in geology, in physiology, in biology. Because no one ever
saw a stone or other so-called inanimate object roll up hill, or
do something which an animal might do, it was thought to be
unable to do anything, whereas every one knows and always
has known that it would roll down hill without any agency
different from its own ; also that one of the laws of motion
affirms that action and reaction are equal, and if one kicks such
a stone, it will kick back in return. Experience of each one of
us teaches the temerity of the action. A lump of coal and a
loaf of bread might lie in one place indefinitely long ; but would
that imply they were inert things and without energy or ability
to do anything.!* No; it would only imply that whatever energy
they might have would not show itself by a change of position
of the whole body. The loaf of bread is made up of particles
of carbon, hydrogen and oxygen with a trace of phosphorus,
sulphur, lime, and three or four other elements in less quantity
still. If eaten by an animal it will furnish it with energy for
doing various kinds of work. If fed to a steam engine in a like
manner it will raise weights or propel itself. If it furnisJies
energy it must be because it has energy ; and if it has energy
it is not inert. In a like manner the lump of coal has energy,
for, if fed to a steam engine, it enables the latter to do its work.
If the lump weighs a pound it is capable of doing ten millions
of foot pounds of work, which, if applied to itself, would raise it
two thousand miles high. Can a body which possesses such an
amount of energy as that in any form be called an inert body .-*
The trouble in thinking of such phenomena is here. Evidences
of energy have been looked for only in the ability of a body to
do a certain thing, namely, change its position. Let a man be
sleeping soundly and he does not change his position. If he is

HOW PHENOMENA ARE INTERPRETED. "JJ

to be moved, others have to do it, but no one would think of
calling a sleeping man inert. For the time being he is unable
to use his energy in that particular way, and energy may exist
in many different ways. The smallest particle of coal we can
see in a microscope possesses its proportional part of energy of
that kind, and one must perforce assume the same things true
of the atoms of carbon ; but that is the same thing as saying that
carbon atoms are not inert things, and the same thing is to be
said of oxygen, hydrogen, and the rest. And there is no evi-
dence that any kind of a physical process could ever extract all
its energy, for there is the best of physical evidence that atoms
of all sorts are not only indestructible by physical processes,
but that they possess inherent energy, and are also able to
absorb other energy to a perfectly unlimited extent from the
medium in which they exist, namely, the ether ; also that they
react upon the ether because of their own inherent energy.
Observe in all this that I am talking about matter in its atomic
forms, not as foreign bodies acted upon by this or that kind of
energy, but as being themselves the very embodiment of energy
and reacting in every case in accordance with the law of
energy.

Physical philosophers had sufficient data for all this long ago,
but their philosophical preconceptions prevented its significance
from being seen until Joule, Faraday, Helmholtz, and a few
others developed what is called the doctrine of the Conser-
vation of Energy. Even with all the evidence we have to-day,
there are many physicists and chemists who follow afar off.
Some are afraid from religious convictions, others are not
interested in fundamental questions at all, and so pay no at-
tention to them ; still others are muddled with terminology,
which is frequently misleading, and such try to convince them-
selves and others that not so much is known as is known.
The outlook is not such as they expected, and the interpreta-
tion is so far from their hazy ideals that the new knowledge
and all its implications are repudiated without being appre-
hended. If matter and its relations are not what they have
been believed to be, and if the growth of knowledge has been
steadily away from the older conceptions, so that not a single

yS BIOLOGICAL LECTURES.

one of them has been verified in physical science, there is left
the strong presumption that the remainder will turn out to be
as far from the truth as have those which are already settled,
if, peradventure, anything can be said to be settled.

Perhaps most persons who are satisfied with the modern
doctrine of phenomenal relations and are willing to concede
that our notions of the constitution and nature of matter
needed revision, and who do not object on any ground to the
physical interpretations and explanations, may feel and say :
" Granted all you say about the whole of physical science, that
matter itself is not what it was thought to be or to be like, even
to the extent of being alive in some measure, it would not fol-
low that matter as such could feel or think or know, and this
is what the whole contention is and has been about, not whether
the physical constitution of things is thus or thus. There is
no evidence that matter as such is intelligent." This is a judg-
ment as to the nature and possibilities of matter based on some
a p}iori philosophy, not upon a study of the thing itself. Who
are they who make such an assertion } Those who know most
about matter and its possibilities .<* Any one who could stand
an examination upon the subject for five minutes.-* I think not.
Such may have feeling but not knowledge for this belief. If
one is to explain phenomena on the basis of what is known, if
all kinds of phenomena are necessarily interrelated, then it is
proper to ask if there be any evidence that such activities as
feeling, knowing, thinking, exist apart from material structure t
As a matter of fact is it not entirely true that wherever there
is evidence for either there is abundant evidence for material
structure.'* If such matter be inert, as has been so long assumed,
then it was a fair inference that something other than its own
resources must be summoned in order to account for any kind
of a happening. If, on the other hand, matter be not inert but
endowed with energy, then what matter can do and what may be
expected of it need further looking into, as is indeed the case.

If what I have presented has any proper warrant in fact, there
is then a warning to be heeded against assuming on limited
knowledge what are the possible properties of matter and assert-
ing what it cannot do. The difficulty of forming any concep-

HOIV PHENOMENA ARE INTERPRETED. 79

tion of how such unlike phenomena as feeling and material
movements can be related is great, but we have plenty of evi-
dence that we have grown into conceptions which are apparently
as unlikely as these. For instance, what possible relations
can there be between turning a crank and that which is
called electricity, which travels in a wire or in an empty
space with the velocity of 186,000 miles a second, glows like
the sun in an arc lamp, and will serve for a chat with a
friend in Chicago as if you were face to face. Yet there
is now known to be a direct and quantitative relation, and the
explanation of the whole thing lies in the properties of the
atoms themselves — properties which were unimagined not
a long time ago. So as knowledge has advanced the whole
drift of it has been to enlarge the possibilities of matter itself,
and this reflection serves to make it more and more probable
that all the other phenomena exhibited by matter are due to its
inherent qualities. We must wholly discard the old view of it
and adopt a larger view. One must ask again what is the pos-
sible nature of matter, and can any one tell enough about it to
help on a step in the process, — especially to bridge such a
chasm as appears between mind and matter }

We do have a new conception of matter which is now so well
vouched for that both the physicists and chemists are inter-
preting phenomena by its means. This is that the atoms of
matter are vortex rings in the ether and made of ether itself ;
they are simply whorls of ether and are not something else
created in ether, and all the properties it manifests are due not
more to the structure than to the stuff it is made of ; and if this
be the fact, the whole controversy concerning matter and its
properties and possibilities becomes a controversy about some-
thing else than matter, namely, the ether. It is discovered that
the characteristics of matter do not belong to the ether, and
that nearly, if not all terms we use to describe matter phenom-
ena are wholly inapplicable to the ether ; indeed, we are without
proper terms to describe them. Matter as we know it is made
up of particles ; ether is not. Matter is more or less porous ; the
ether is without interstices, — it is called a continuous medium
and is boundless in extent. Matter is subject to friction, and

8o BIOLOGICAL LECTURES.

all mechanical movements of it are soon brought to rest. The
ether is frictionless. Matter has gravity ; the ether is without
it. Hence it is plain that one must not include ether when he
is talking about matter, for it is altogether a different some-
thing with different and unknown and undiscovered qualities,
and no one has been able to deduce the properties of matter,
as we know it, from the properties of ether. It is plainly the
agency by which light and heat get to us from the sun and stars,
by which electric and magnetic phenomena become apparent.
Gravity is chargeable to its pressure instead of to the attraction
of matter. It transmits wave motions at the rate of 186,000
miles a second, but it transmits gravity more than 200,000 million
miles a second. Some of the phenomena it exhibits seem to
show it to be an enormous storehouse of energy, — one million
horse power per cubic foot is a low estimate for it. Like astro-
nomical distances and magnitudes it may be computed but not
conceived. With all this it is entirely incapable of affecting
any of our senses. We are without any nerves capable of per-
ceiving it, and belief in the existence of such a medium has
been forced upon men of science because, first, every former
supposition has experimentally broken down ; second, because,
as Sir Isaac Newton said, it is impossible to think that one
body can act upon another not in contact with it without some
kind of a medium between them ; and lastly, because energy does
get from one body to another in the absence of ordinary matter,
as is exhibited by the heat and light of the sun, and the rate of
transference can be measured in several ways. The interpre-
tation of the physical facts observed has necessitated it, and by
its means otherwise inexplicable diflficulties are overcome. I
think there is not a physicist of any nation or rank who has
attended to the facts, who is not satisfied of the existence of
what we call ether, but no one can describe it or tell how it can
and how it does act upon matter. We are in almost total igno-
rance about it. If it is hazardous to set limits to the possibilities
of matter with the advantage of what knowledge we have of it,
what shall be said of the attempt to limit the qualities and
possibilities of what we know nothing about, — ether! The
mystery of matter is great, but is nothing to the apparent mys-

NOPV PHENOMENA ARE INTERPRETED. 8 1

tery of the ether ; and if matter be, as I have hinted, a particular
form of energy in the ether, then what can happen in matter
depends upon the wholly unknown possibilities of the ether.
Again, if the phenomena exhibited by matter lead to the con-
viction that the latter is made up of the fornjer, then logic leads
to the necessary assumption that the ether must have existed
before matter, which is made out of it, and so far such a con-
clusion finds favor with all philosophers. In physical philoso-
phy a phenomenon is said to be explained or interpreted when
its antecedents are all pointed out. When such antecedents
are unknown we strive to discover the missing factor, always
assuming that whatever it may be it has some necessary relation
to the phenomenon which, when discovered, may be made
intelligible in the same terms the rest have been. Note how
this applies to the explanation of the existence of matter itself.
A uniform, homogeneous, frictionless, gravitationless medium,
such as the ether appears to be, could not itself organize a
single vortex ring possessing energy, which should be the in-
destructible thing an atom appears tQ be. Mechanical actions
such as belong to our scientific scheme of knowledge are abso-
lutely powerless in a frictionless medium, and in order to pro-
duce such a thing as an atom there is needed an activity
altogether unrelated to any kind we know or which has ever
been the subject of consideration in physical science. Creation
is the only word which is suitable for the action, and there is
implied behind the ether some other factor not necessarily related
to it in the sense in which ether is related to matter. So that
behind both matter and ether there is a something which must
be postulated as the initiative of all we see and know, capable
of acting upon the ether, but without mechanical compulsion.
Therefore choice, a mental attribute, has a locus here, and mind
appears to be a necessary assumption, as necessary for a proper
antecedent as is ether pressure for the phenomena of attraction
or an artificer for making a house, and this, too, wherever there
is an atom, whether here upon the earth or in the most distant
star, — everywhere, omnipresent mind. Choice implies con-
sciousness and intelligence, and so physical interpretations of
the phenomena always before our eyes lead us back to a super-

82 BIOLOGICAL LECTURES.

physical beginning. If we find energy in the form of matter,
it is not necessarily there. If we find life in it, it is because
mind is operative in all ether and therefore in all matter, and
cannot be exorcised from it. Some philosophers speak of this
as ** infinite and eternal energy," but it is not such energy as
the physicist measures in foot pounds. Other philosophers
call it God, and can one express in terser, truer or more
scientific language the relation of mankind to this infinite power
than did Paul in Athens : " In Him we live and move and have
our being."

SIXTH LECTURE.

KNOWN RELATIONS BETWEEN MIND AND
MATTER.

A. E. DOLBEAR.

We have a body of knowledge which we call science. In a
few — a very few — instances it is so far perfected we can use
it for prevision, and thus we make almanacs, learn when the
moon will be eclipsed, and when the tide will come in, how to
make a steam-engine or a dynamo to do a specific amount of
work, and so on ; but for nearly every question in which
humanity, as a whole, has an immediate interest there is now
no satisfactory answer, which, broadly stated, means that there
is yet no science which can be applied to them in the same
sense as it can be applied to astronomical problems. The best
one can do is to hold any opinion very gently, and be ready to
abandon it at once if occasion comes.

"The science of life," — that is what we all want to under-
stand in order to get the most out of it. That there is a
possible science of life everybody believes. In every great
emergency among men there are always a number of persons
who are ready to tell us about it, and what should be done to
avoid catastrophe. When Jerusalem was in a state of siege
there were several who claimed to be the Messiah, each promis-
ing deliverance if the people would but hearken to them ; but
in the multitude of such Messiahs, how could one judge which
was the true one except he should actually deliver them from
their troubles, whether they believed in him or not ? The test
for one's ability is what he does, not what he promises to do.
So there are teachers and preachers and makers of books who
tell how it is, and what to do, yet we are no wiser, and society

84 BIOLOGICAL LECTURES.

is troubled with trusts, monopolies, strikes, theories of taxa-
tion, of protection, of values, of liberty, of free-will, of the
family, of education, of heredity, of life itself ; and who shall
deliver us ? To say that science will may be true enough, but
she cannot to-day.

In his Locksley Hall Tennyson wrote more than fifty years

ago: —

" Science moves but slowly, slowly,
Creeping on from point to point."

And that was true then, and in large measure is true to-day,
concerning all those matters that relate more nearly to us in
our everyday lives. When we laud science, and tell how
much has been accomplished within the past fifty years, it is
just as well to remember that what has been achieved in this
domain has been mostly in the purely mechanical field. We
feel quite sure we now know how the Solar system came to be
as it is, — through a series of slow changes by which a huge
molecular cloud of dust in space becomes a body of rotating
globes revolving about a central hot mass. We feel quite
confident that what we call the doctrine of energy is true, and
that it is not created or annihilated by any processes in our
experience. We are almost, if not quite convinced that the
animals and plants upon the earth to-day are the descendants
in unbroken line from the simplest microscopic forms of living
things in the far off geologic ages, and we put all these things
together and call the process of becoming something different,
— evolution ; and for convenience we call some mechanical
science, and some molecular science, and some biologic science,
according as the subject-matter is among big bodies or little
bodies or living bodies. But it is sometimes forgotten or
overlooked that the same forces are at work with the little as
with the big bodies, and that no body, large or small, can be
separated from the action of all the rest, and that no particle
of matter ever lets go its grip on any other one. These things,
I have said, we think we know ; but may I not say we do know,
if we really do know anything.? If there be any doubt about
gravitation, about the laws of energy, about the multiplication
table, then one may harbor doubts about any thing he pleases ;

RELATIONS BETWEEN MIND AND MATTER. 85

and there is justification for even this doubt. Have not the
mathematicians lately told us emphatically that there are no
axioms, that all once held as absolutely true about lines and
angles — in short, geometry — has no better basis than experi-
ment and the narrow limits of our experience, thus bringing our
rational powers to a standstill in the presence of problems out
of the range of our instruments ? This is precisely what has
been done, and for all we know the universe may be a very
different thing from what it has seemed to be, for in concluding
what it is we have always assumed that space was what it
seemed to be, and that ideally one could go in a straight line
on and on forever. Now we do not know that, say the mathe-
maticians ; and they talk of space of four or more dimensions
where our laws of physics and energy will not hold. And
more than that, some of them begin to derive comfort from
the reflection that, after all, the universe is not half so simple
and easy to understand as they had once thought, and that the
possibilities of knowledge and of existence may vastly exceed
" anything any one has yet imagined. For us, then, science
must be correlated experiences^ and for us the truth can only be
that statement which is in accordance with the best and most
certain other things we know ; it must be in accordance with
our geometry, our energy, with our modes of thought, and then
always with the reservation that what to-day seems funda-
mental may ultimately turn out to be derived, and relations
that seem obvious may be far from it.

All this is a sort of disclaimer against being taken for
one who believes and teaches that the knowledge we have
is sufficient to enable him or others to deduce all phenom-
ena, or even to foresee in any kind of way how to answer
properly many of the questions which concern us all. The
decalogue was mostly a compendium of dotitSy and the best
that such science as I have knowledge of can now do is
to tell us what not to do, rather than what at once to do,
and gives a mere hint as to the direction one must look for
further light on any or all of them. Of course we all know
how men have speculated on both mind and body and their
relation, and it has always been quite the fashion to go into

86 BIOLOGICAL LECTURES.

the history of the steps in thought from the earliest time till
now when treating on this and kindred topics, — a course
which implies there has been some kind of progress, and
that each generation has contributed in some degree to the
solution. It hardly needs to be said that this is no more true
in this matter than in any other of the sciences. In astronomy
one 'need not go back of Copernicus. In chemistry one need
not go back of Dalton. In electricity one need not go back of
Franklin ; in heat, back of Sir Humphrey Davy ; in biology,
back of Darwin. Not that there was nothing known before
them, but what was known was of little and no importance.
If all biologic knowledge before 1840 were subtracted from
present knowledge, it would scarcely be missed ; and if in these
fundamental things there was nothing of importance, still more
true is it in the more difficult and unexplored field of mind and
its bodily relations. There is not a single philosopher from
Adam, and the year i up to 1850, whose knowledge and
opinions on the question are worth a hearing ; and all refer-
ences to the expressed or implied statements of any of them,
as having any weight at all in the settlement of any of these
questions, seem to me to be utterly useless, — as useless as
their speculations on the habitability of the planets. None of
them had adequate data ; in fact, they knew nothing about it.
If, also, one remembers that modern knowledge is not ancient
or mediaeval knowledge confirmed and expanded, but new
knowledge which contradicts and repudiates most of the old,
he will see still less reason for appealing to antiquity for the
support of any doctrine. Now, seeing that the theologians
have admitted that the Bible was given for instruction in
religious things, not in science, it is no longer safe to quote
scripture as a warrant for any opinion upon a question involv-
ing scientific data or method ; hence, even on the question of
mind and body no one looks there either for direction or
corroboration.

By body we mean the matter which constitutes the animal
mechanism, as that which embodies the various functions of
growth, assimilation, movements of one kind and another, and
along with these exhibits, in some degree some order of intelli-

RELATIONS BETWEEN MIND AND MATTER. ^J

gence. Once there seemed to be sufficient reason for dividing liv-
ing things into plants and animals. That was when knowledge
was fragmentary ; but now there is no line between them,
and no naturalist can so define one as to exclude the other.
The possession of what is called irritability, by which is meant
ability to respond by movement of some kind to an external
stimulus, is no longer a peculiar characteristic of what have
been called animals, for there are many plants that possess it
in a marked degree ; and there are free swimming plants, such
as bacteria. Experimental research with the microscope has
shown that this quality exists in all plants in some degree, and
that in all cases the reaction, of whatever kind it may be, shows
evidence of what, in higher forms of living things, is always
attributed to intelligence; that is, the reaction is adaptive.
This does not mean what in higher living things we call choice,
but it does mean that the energy resident in the organism
works spasmodically, automatically, and mechanically in a very
wonderful manner, and gives rise to phenomena which have
been thought could only appear where there was some kind of
animal existence as distinct from a vegetable. The discovery
of sensitivity as a quality belonging to all plants is new, and
makes it still more important that one should inquire further
as to whether other distinctions are as real as they have been
thought to be. Once a vital force was believed to be resident
in living things, and this force was supposed to control diges-
tion, nutrition, growth, and feeling," but all biologists have
discarded the idea. I do not know of a single naturalist of
any distinction in the world who does not think and say that
all the phenomena exhibited by plants and animals are due to
physical and chemical causes alone. In a late lecture Professor
Stokvis, of Amsterdam University, said : " Certain it is that
life is a chemical function," and he thinks it is proved beyond
a peradventure. To present the evidence for it would be to
make a book ; and seeing that it is so generally accepted in
scientific quarters, where it would first meet opposition if it
could be opposed, one may accept it, — at any rate, provisionally.
But what is meant by life } Well, in brief, it means the
sum of the activities possessed by living things, including

88 BIOLOGICAL LECTURES.

growth, assimilation, reproduction. If such qualities are really
only refined physics and chemistry, as has been stated, then is
it much matter for wonder that our predecessors did not find
it out, seeing that they had no knowledge of either ? Now, the
outcome of what is called life, even in the lowest and so-called
insensate forms, is wonderful enough, and is so different from
what has been supposed to be possible to mere matter, that it
is worth the while to stop and consider why it has seemed so
different.

The philosophers in all the past have had a kind of theory
of things to maintain, as to how man came to be on the earth,
and especially how evil came to be his portion. Man was
created upright and good, but by transgression he fell, and the
earth with him was cursed. This theory required the concep-
tion of the matter or material of which the earth is made as
being utterly inert and dead. The idea was that life, as we
know it, was breathed into it, and not until then was there any
living thing. Matter was not only lifeless, but it was gross,
and all sorts of epithets were applied to it to make wider the
distinction between it and a living thing. From a dictum it
became a belief ; and, although there was no one who could
prove it, or took any steps to prove it, it came to be considered
true, and the proposition that matter had no power to do any-
thing by itself was thought to be almost axiomatic, and that in
spite of the wonderful succession of all kinds of phenomena
witnessed every day, — combustion, the falling of an apple,
the formation of clouds and dew and hail, the recurrence of
day and night, the explosion of powder, of gas, and others just
as well known, all showing that matter, so-called inorganic
matter, did in some way possess active properties of certain
kinds by which it could change phenomena solely through its
own powers. It is endowed with energy. Mix sulphur, carbon
and saltpetre together — the mixture you call powder; but you
are aware that the compound possesses tremendous energy
which you have not imparted to it ; and so does all matter —
every atom of it — possess energy of a kind that enables it,
under proper conditions, to do the most wonderful things ; and
yet this was not suspected for thousands of years, and even

. RELATIONS BETWEEN MIND AND MATTER. 89

after it was discovered it was not perceived for a long time
that the inertness of matter could no longer be held as a tenet
in philosophy. There are plenty of teachers yet who think
matter to be inert, and as possessing no energy. But what is
energy } Simply the ability of a body to act on other bodies
so as to move them in one way or another.

That kind of action which is called chemical action, by which
atoms combine together in certain definite ways, in which
atoms choose their partners and become wedded, is a manifes-
tation of the energy of atoms, which is ever present with them,
a part of their endowment and inalienable. Heat, light, elec-
tricity are modes of the energetic action of the ultimate parti-
cles of matter called the elements. In all the manifestations of
these so-called forms of motion or energy, which we employ for
economic uses, it ought not to be forgotten that we do not
endow the matter, but we find it already endowed, which shows
that matter is not to be considered as so helpless as it has been
the custom to think it to be. But these atoms and their com-
binations— that is, molecules — are often found organized into
beautiful forms called crystals. There are diamonds and sap-
phires, rubies and emeralds, garnets, topazes, beryls, sugar, alum,
and a thousand forms familiar enough everywhere. These
symmetrical forms are due solely to the inherent qualities of the
substances themselves, and testify to the ability of the matter
to arrange itself, which inert matter could not do. Dewar and
others have shown that in the absence of temperature, chemism
does not exist ; and if matter can do so much as is plain to
perceive, is it likely that these exhaust the possibilities of its
doings } We know better already ; but I have developed this
point far enough to show what I want to make plain, namely,
that matter has possibilities which the reigning philosophy has
denied it to have.

It has been the custom to speak of all the inherent qualities
of matter and the various phenomena which directly result from
them as being physical and chemical. Are there any such
purely physical and chemical phenomena that are really com-
parable with what we take to be vital or living phenomena }
Yes, a great many.

90 BIOLOGICAL LECTURES.

Let a crystal, say of quartz, have an end or a corner knocked
off. If it now be placed in a solution so that growth can go on,
the crystal will mend up its defacement so as to be symmetri-
cal before it will be enlarged elsewhere, just as a spider will
grow a new leg if the old one be removed. The cases are sim-
ilar. There are so many and so great a variety of such activ-
ities in matter that, from the physical side, men have been
forced to conclude that matter is itself alive, every atom of it,
just as the biologists from that side of the study have con-
cluded that life is a chemical and physical process simply.
There is agreement here. With such a conception of matter,
one cannot look at any object whatever without increased
respect for it, for not alone the animal or insect which is called
living possesses the distinguishing vitality, but the very air we
breathe and the dust under our feet. The food we eat endows
us with life because it has it, not that it creates it. We eat it
and drink it and breathe it, and withal, life in this view is here
and always has been. There is no need for a miracle to pop-
ulate the world, and every star and satellite is inhabited, — yea,
is a living thing itself, the degree of complexity of such life
depending solely upon the possible complexity of chemical
organization. This is an inference, of course, but it follows
from the premises without any circumlocution.

By body, then, we mean a local habitat for a living thing. We
also mean the living thing itself, whether it be large or small ;
and seeing there is no special limit to the magnitude of a body
which possesses this quality, and that there is good reason for
holding that matter is itself alive, it is apparent that it is now
of importance to know still more of that thing we call an atom,
whether it be of one kind or another. We all know what the
text-books say about its properties, as of weight, hardness,
density, elasticity, impenetrability, and so on. It will be remem-
bered, also, there are known some seventy different kinds of
elementary matter. If one will stop an instant to think, he will
see that differences in size or shape cannot account for such
differences in quality as are presented by the elements. One
might make of wood seventy different sizes and shapes, but the
density, hardness, elasticity, and so on would be the same in

RELATIONS BETWEEN MIND AND MATTER. 91

all. So there would be needed as many kinds of elementary
stuff out of which the atoms were made as there were kinds of
atoms, and this complicated process and material has no degree
of probability at all, for the physical evidence we have an abun-
dance of to-day all goes to show that nearly, if not quite, all the
physical qualities of the elementary atoms is due to the quality
of their motions and to nothing else. There is not time to
enter upon this phase of the question, but it is true that physi-
cists have been led to this conclusion which I quote from Karl
Pearson's work on The Grammar of Science: "The whole
tendency of modern physics has been to describe natural phe-
nomena by reducing them to conceptual motions" ; also, "Hard-
ness, weight, color, temperature, cohesion, chemical constitution
may all be described by the aid of the motions of a single
medium which itself has no hardness, weight, color, tempera-
ture, nor indeed elasticity of the ordinary type." If such a
view of the subject-matter be true in any sense, then one sees
at first glance that what one means by body — that is, visible
masses made up of this kind of matter — must be very
different from what is involved in the ordinary conception
of it, and life must be very different in its nature from
what it has so long been held to be. As such matter
as is described above cannot be created nor annihilated
by any physical or chemical process yet discovered or even
imagined, its very existence is a guarantee of all of its so-
called qualities, even life itself, and we come in sight of a fact
of tremendous importance to every individual who has tasted
the sweets of existence and who feels loth to give them up,
especially when he sees creation is so large, its possibilities of
gratification so boundless, that probably millions of years have
been spent in leading up to him, which, if he is to cease con-
scious existence at any time, will apparently have been wasted
with little or no profit to any. Some have hoped that what is
called this life is not all, and they point to this or that as evi-
dence for their hope, but there has been a total lack of physical
evidence for such an issue. No one who knows anything about
matter doubts that an atom of, say carbon, is practically an inde-
structible thing ; that its properties were the same a million

92 BIOLOGICAL LECTURES.

years ago as they are to-day, and will be the same a million years
to come ; and if one knew it to be a living thing now, he would
expect it to remain a living thing, and if it were conscious, that
it would continue to be conscious. Another important consid-
eration lies here. The so-called properties of matter are not
detachable from matter itself. One cannot separate heat or
weight or vitality from a mass of matter ; they are not entities,
they are qualities. Set a top spinning and how wonderfully
it behaves. It will stand on its point and hum, or sleep, as the
boys say; but touch it ever so gently, and how it will bound
away, and do the most unexpected things. It is the motion it
has which enables it to act thus, and one who did not know
that the sleeping top was in motion, and should notice what it
did on being touched, might fairly well think it had a spirit in
it. But no one can detach the spin from the top so that he
could hold the spin in one hand and the top in the other ;
neither if life be such a material property can it be detached
from what embodies it. If one ties to physics at all he must
not play fast and loose with it. It will not do to take this and
reject that because it does not meet our likes or wishes. There
is no evidence I am acquainted with that physics acts conjointly
with anything else. Whatever it does, it does on its own
responsibility, and the result is to be measured on its own
balance. This is equivalent to saying that the field of physics
is much broader than has been supposed. When Newton
lived, physics had to do only with the movements of large
bodies. In our time it has been carried down to atoms, and, as
I have said, the knowledge here gained has been not simply an
extension of the old, it has been revolutionary in its bearing on
all questions, and the glimpses it has given of present outlying
fields convinces one that there must soon come such a hegira
from the old schools of thought as has never been witnessed,
although the past thirty years shows that in the field of natural
history everybody has changed from a creationist to an evolution-
ist. But this has been only the beginning of the change, for
if that science was true that made such a change necessary, it
is also true that the same science will make needful other
changes in men's conceptions of what kind of a universe they

RELATIONS BETWEEN MIND AND MATTER. 93

live in, how it works, and how they came to be and to think
as they do ; and not unlikely what we please to call evolution
will have to be explained and restated in very different terms
from those in vogue now.

So far I have talked about body and have endeavored to
show that present science gives no warrant for holding that
the matter which constitutes it is lifeless or inert ; but, on the
other hand, it does show that it is endowed with energy, and
that in enormous quantity, and also that the minute study of it
has led students from both the biologic and physical side to
conclude that matter is itself alive, as endowed with an inalien-
able quality, and that the manifestations of this quality depend
upon the degree of complexity of composition and arrange-
ment rather than upon any superendowment of any kind of
an entity, and hence giving no support to the notion of a disem-
bodied spirit, in the extreme sense of that expression. How
much matter is really needed to exhibit any degree of life }

Let us turn now to the other factor, — mind. First it may be
remarked that there is no tangible evidence of the existence of
mind apart from some kind of a material structure. I suppose
there is no one now who would imagine that in the develop-
ment of, say a chicken, there came a time in the physical and
chemical changes going on in a warm t^^ when it was in
some superphysical way endowed with what we call mind in
any degree, so that one could say, now this growing thing is
without mind, and the next instant, now this growing thing
has a mind. If mental endowment be not a part of the
physical process just as necessary under the conditions as any
other part of the process, then one must say at some instant,
7tow it has been endowed. The chicken in the ^g^ has life,
for it grows, and when out of it gives evidence of intelligence
of no mean grade. Whatever its grade, it is the outcome
either of its physical constitution or else there has been a
miracle of some order. Is there any third alternative t I
know of none. That there has been a miraculous phenomenon
in the ^gg^ no one can believe, and that the intelligence is the
mere outcome of physical antecedents few want to believe.
If one believes that humanity, as it now is, is traceable

94 BIOLOGICAL LECTURES.

without miracle into geologic times, that in some kind of
a way all degrees of intelligence are directly related, then
what in its degree is true for a chicken is also true for
man, and mental endowment is no more miraculous for one
than the other ; and one must need to look for his so-
called faculties where he must look for those of the chicken
or the dog, namely, as the outcome of the original endowment
of what we call matter, rather than as a supernatural alliancQ
with matter which is the common notion. Already enough is
known as to the material dependence of the mind upon the
body to warrant even judicial acts to be based upon chemical
analysis of bodily products ; that emotions of different kinds
yield corresponding chemical substances. Some of these pro-
ducts are harmful in the extreme, some poisonous, while
others are healthful and promotive of life. Brain building is
the end towards which this new science is reaching. One of
its axioms is that the mind can only be educated through the
senses, and the more senses and the better they are developed
the more mental power. Thinking is the function of gray
cellular matter that covers the brain like the rind of an orange.
Unconscious thinking vastly exceeds in amount our conscious
thinking. When thinking and doing have been repeated often,
they cease to be conscious acts, — they become automatic, in-
stinctive, and seem to sink out of conscious personality ; but
they may be summoned. So that unconsciousness makes the
most part of our lives. The individual starts with a bundle of
instincts, that is, inherited experiences, all unconscious, but
yet the product of consciousness ; and consciousness that has
all come from and through nerve action. All this may be so,
and yet the question still could be asked, are mind and matter
separable } One might point, as others have frequently done,
to the evidence of the growth and decadence of the mind along
with the growth and decadence of the bodily functions, of the
impairment of mental activity and quality when the brain or
stomach or liver is impaired, and full recovery when these are
brought to normal conditions again ; also how the individual
lives over in himself the history of the race, as a mere animal
at first, then a savage, and lastly as an intellectual and moral

RELATIONS BETWEEN MIND AND MATTER. 95

being, — a condition of things that educational theories and
practice ignore or overlook when they attempt to make a moral
and intellectual being out of one in his savage stage of exist-
ence, as if one should try to make the caterpillar live on the
honey of flowers and fly, when as yet it had neither the
instincts nor machinery for such a life. Feed him what he
wants and can digest, protect him from enemies of all sorts,
and let him otherwise alone. If nature intended him to fly,
his wings are growing, though they may be folded so as not to
be discerned and no use is made of them. Let them alone.
If she did not thus intend him to fly, no food nor training nor
painstaking will give him wings and he will never fly. This is
a by-path.

To everyone who has thought and read on this subject of the
relation of mind to the bodily organism, especially in the last
few years, there appears at once the question of the relation of
the doctrine of the conservation of energy to mental action,
the question of free will and the question of automatism. I
have not heard that any one actually disputes the doctrine of
the conservation of energy, which means that energy is not
created nor annihilated by any kind of a process known to
us. Let me quote the words of Hoffding in his OiUlines of
Psychology as bearing on this point : *' In the nature of the
case only four possibilities can be conceived : (i) either con-
sciousness and brain, mind and body act one upon the other
as two distinct beings or substances, (2) or the mind is only a
form or product of the body, (3) or the body is only a form or
product of one or several mental beings, or finally, (4) mind
and body, consciousness and brain are evolved as different forms
of expression of one and the same being." He then presents
the arguments pro and con on each of these, and at last thus
concludes : *' Only the last or the fourth possibility then seems
to be left. We have no right to take mind and body for two
beings or substances in reciprocal interaction. On the contrary,
we are impelled to conceive the material interaction between
the brain and nervous system as an outer form of the inner
ideal unity of consciousness. Both parallelism and propor-
tionality between the activity of consciousness and cerebral

96 BIOLOGICAL LECTURES.

activity point to an identity at bottom," and he italicizes identity.
Such statements from such a source show that even psycholo-
gists of the experimental type have been driven to conclude that
mentality and physical activity are not different things, but
opposite sides of the same thing, which is saying in another
way that mind is as much a function of matter as is gravitation,
or as magnetism is of iron, — cannot be created nor destroyed
nor isolated, but may be obscured in various ways. To say
that one cannot conceive how mind can be so related is not to
say much. Can any one say he can conceive how mind, as he
imagines it, can exist in a body at all } And does one need to
wait until any matter is fully explained before he can assent to
what is known about it t Thus the existence of dynamos and
motors and electric lights and telegraphs and telephones is in
itself sufficient to prove that we know a great deal about elec-
tricity, the conditions for its generation and utilization ; and
when one adds to these the knowledge that dynamos and
motors can be made at will, having an efficiency of 96 or 97^,
he has as high a guarantee as one can have for anything in
this world that no man hereafter can improve on our electrical
apparatus by as much as 5^, and all this without pretending
to know or even guess how it is that electricity can do any-
thing, much less have a knowledge of its ultimate nature.
These may come in due time. Meanwhile one need not be
skeptical as to how much is known — really known — about it,
because he cannot an^jver the very last question which may be
asked about it.

What, then, is the present status of the question } In our
experience mind is associated with matter always, life as we
know it is always associated with a particularly complex chem-
ical substance ; and when, for any reason, this substance of
life is disintegrated, the evidence of life goes too. The more
complicated the material organism, the more complicated the
manifestations of life and of mind.

The delight in the consciousness of existence has led man to
wish for its continuance and to cast about for evidence of it.
The apparent destruction of mind with the disintegration of
the body has led men to think there must be some fallacy

RELATIONS BETWEEN MIND AND MATTER. 97

somewhere ; and so they have asserted that the body is but a
temporary habitat for the mind, or soul, as it is often called,
and that the soul could and did exist independent of matter
in any of its embodiments, so the conscious being has been
imagined as an immaterial something, very much as heat and
light and electricity have been supposed to be immaterial
somethings. By and by heat and light and electricity were
each shown to be no such kind of things, and as having no
existence apart from ordinary matter. After that, vital force
as differing from chemical and physical forces was dispensed
with, and next both biologist and physicist agree that life is, in
all probability, but a function of ordinary matter; and lastly
the psychologist brings in as his return that mind and matter
are but the two sides of the same reality. This does not mean
what it has generally been taken to mean, but exactly the
opposite. It has been held and taught by many that to asso-
ciate either life or mind with matter as a necessary adjunct
was pure materialism. Some have thought that if the doctrine
of the conservation of energy were true or were admitted to be
true, 'then life would be correlated with the other forces as
they are correlated with each other, so that whenever one
appeared it was at the expense of and destruction of some
other, — as when heat energy is changed into work or into
electrical energy. But the analogy is wrong. It would be
nearer correct to liken it to, say magnetism of a piece of iron.
For convenience we say we magnetize a piece of iron. In
reality we do nothing of the sort, — the iron is already as mag-
netic as it can be ; all we do is to arrange its molecules so that
the inherent magnetism of each one will act in the same direc-
tion as all the rest. There is as much magnetism in a piece of
iron at one time as at another; we cannot change that. To
carry out the analogy, if one would suppose that when the
atoms and molecules of matter are of proper sort and arranged
in a proper way, as they are in the substance called protoplasm,
then the individual living characteristics of each could manifest
themselves in the way exhibited by a living thing, not because
there was a new force or being or entity not there before, but
because all could work in concert to the same end, while they

98 BIOLOGICAL LECTURES.

cannot under ordinary physical conditions. In other words,
there is nothing which was not there before. One is not get-
ting out of the machine what was not in it, but what was in it,
and there is no quarrel with the doctrine of the conservation
of energy. That doctrine, if true, would only insure conti-
nuity, regularity, and certainty of dependent relations.

Still more than this. It is important to recognize how much
energy there may be in a microscopic mass of matter, and also
what an amount of intelligence may be there too ! Think of the
intelligence shown by a common ant : he lives in a community
having common interests, and where the duties of individuals
are appointed and faithfully executed, — duties of securing
food, of protecting and caring for the young, of defending the
community as a whole. They make war, and slavery is the
price of peace ; they have a language of some sort and a
degree of civilization superior to some tribes of men, and all
this the outcome of a brain so small that no balance we have
is delicate enough to weigh it. It is plain proof that if mind
does require some material habitat, its requirements are not
excessive ; indeed, if one will remember that in a mass of mat-
ter only the thousandth part of an inch in diameter there are
thousands of millions of atoms, he will see that the possibility
of variety of form, of position, and of relations is almost infinite,
and if mind depended upon these in any measure, the possi-
bilities would also be nearly infinite. There is nothing in all
this that implies that what is called death ends all, — rather the
contrary, for it is plainly in accordance with all we know to
hold that the so-called ego is a real material thing, a mole-
cule too minute to be seen or identified, but which absorbs all
experiences and holds them as memory, which can be disso-
ciated from the rest of the body, but which cannot itself be
disrupted any more than atoms of the ordinary sort can be,
which is as durable as we believe others to be, but differs from
them chiefly in having been ediLcated by being in such a posi-
tion that all sorts of reactions took place in its environment
and in itself.

Formerly mind was supposed to be honored by degrading
its material habitat; now we are confronted with the knowledge

RELATIONS BETWEEN MIND AND MATTER. 99

that matter is not what it was thought to be or to be like, that
its nature is as mysterious as is the nature of mind. In expe-
rience we find the two always associated. Experience leads to
the belief that one of these is imperishable, and we make it
a corner-stone in physical science ; and my thesis is that mind
can no more be sloughed off from it than can gravity or mag-
netism or any other of its inherent qualities.

SEVENTH LECTURE.

ON THE PHYSICAL BASIS OF ANIMAL PHOS-
PHORESCENCE.i

S. WATASJg.

Whatever view we may take as to the nature of vitality, it
is evident that we can know life only through the physical,
chemical, or mechanical manifestations, which an organism
displays at various phases of its existence. Our organs of
sense, which supply directly or indirectly the material of
human knowledge of both the animate and inanimate world,
are only related to force, or are set into a state of excitation
by motion of certain kinds, which we call a stimulus. What-
ever view, therefore, a biological philosophy may lead us to
accept in regard to the ultimate nature of life, our primary
step in the study of vitality must begin with the examination
of its material manifestations.

Among many physical phenomena manifested by the living
organism there are few so striking, and none appear so isolated,
as the phenomena of the emission of light. Thus, Darwin,
in his discussion of some special difficulties of the theory of
natural selection, says : ** The luminous organs which occur in
a few insects, belonging to widely different families, and which
are situated in different parts of the body, offer, under our
present state of ignorance, a difficulty almost exactly parallel
with that of the electric organs," and "it is impossible to
conceive by what steps these wondrous organs have been
produced." ^

1 The present paper is part of three lectures on Animal Phosphorescence,
delivered at the Marine Biological Laboratory at Woods HoU, during the sum-
mers of 1894 and 1895, ^"*^ elsewhere. A monographic account of the subject,
with a full bibliography, will be presented in the near future.

2 Darwin : Origin of Species. «

I02 BIOLOGICAL LECTURES.

But viewed from the standpoint of cell physiology, the phe-
nomena of animal phosphorescence is the result of physico-
chemical changes in the living protoplasm, probably of the
same nature as that of heat production, the only peculiarity of
the former being that it manifests itself in such a form as to
affect the most potent of our special senses, — the sense of
sight, — and the latter, the sense of temperature.

On a priori ground it is easily conceivable that the animal
that produces heat, as all animals can, may just as well produce
light under certain circumstances, for both are but the mani-
festations of the same energy, and can be produced by essen-
tially the same physico-chemical antecedents.

The production of light by the living organism becomes still
more interesting, and appears unique when we remember that
the light thus produced is not accompanied by any sensible
heat.

" You gaudy glow-worms, carrying seeming fire,
Yet have no heat within ye ! " ^

This difference between the light produced by the activity
of the living organism and by the purely artificial process has
also been pointed out by the natural philosopher, Robert Boyle.
In one 2 of his several contributions on the subject he says:
'* That whereas a coal, as it burns, sends forth store of smoke
or exhalations, luminous wood does not so "; and "that whereas
a coal in shining wastes itself at a great rate, shining wood does
not"; and ''that a quick coal is actually and vehemently hot,
whereas I have not observed shining wood to be so much as
sensibly lukewarm."^

The same peculiarity in the light of the living substance has
been recognized by Faraday, Matteucci, Young, Langley, and
Very, and by the last two it has been made the subject of a
beautiful research within recent years.

1 Fletcher: The Elder Brother, act iv, sc. i, 1637.

2 R. Boyle : Observations and Trials about the Resemblances and Differences
between a Burning Coal and Shining Wood, Phil. Trans., No. XXXII, 605, 1667-
1668.

* It is hardly necessary to say that Boyle was not aware of the fact that the
luminosity of the shining wood is caused by the activity of the living organism.

BASIS OF ANIMAL PHOSPHORESCENCE. 1 03

Readers of the Life of Faraday will notice what a lively
interest he took in the luminous phenomena of the fire-fiy and
the glow-worm. The journaP he kept during his travel over
the continent with Sir Humphry Davy in 18 14, when Faraday
was twenty-two years old, makes frequent mention of his experi-
ments with the luminous phenomena of the fire-fly and the glow-
worm. I quote him at length because he correctly surmised all
the results of his later workers, and also because his unassuming
but remarkable record of his observations has escaped the notice
of writers on animal phosphorescence subsequent to the publi-
cation of Faraday's Life. (Italics are mine.)

" On the way home many fire-flies appeared, emitting their
transient light .^ I caught several ; and on arriving at the
house endeavored to ascertain whether the luminous appearance
depended on the life of the fly. I found one apparently dead ;
and separating the part which emitted light from the rest of
the body, it appeared filled with a white glutinous matter,
which, when extended and exposed to the air, shone for about
a minute.

'' I killed a fly suddenly, and separated the matter. It was
shining at the moment I killed it ; but when dead it ceased to
shine. On separating the part and exposing it to the air it
irrimediately shone brightly as when attached to the fly, and
over the whole surface, although only the section was exposed
to the air. It at length became dim ; but on compressing
it, and exposing a fresh part to the air, it shone brightly
as at first, and thus it continued luminous for above forty
minutes. At last it became totally extinct ; and the same
effect took place with other flies treated in the same manner.
It is probable^ from the intermitting and regular appear-
ance of the lighty that it has a dependence on the respiration ;
and at least it is evident that air is suffi,cient to cause this
matter {probably a secretion) to shine. No heat was sensible
to the hands or to the underlip {the most delicate part of the
body)!'

1 Dr. Bence Jones : Life and Letters of Faraday, Vol. I, 1870, pp. 90, 91, 125,
141, 142, 144-146.

^ Friday, June 3, 1814 (Terni), Italy, pp. 141, 142.

104 BIOLOGICAL LECTURES.

In his entry '^ Sunday, July lo, 1814, Geneva," Faraday de-
scribes his experiments on glow-worms.

''This evening many glow-worms appeared, and of four
which I had put in a tumbler with green leaves, two shone
very brightly. I separated the luminous part of one in full
vigor from the body. It soon faded, and in about ten minutes
ceased to emit light ; but on pressing it with a knife, so as to
force the matter out of the skin, it again became luminous, and
continued to shine for two hojirs brightly. One I found on the
floor crushed unawares by the foot. I separated the luminous
part of this insect, and left it on paper. It shone with undi-
minished luster the whole evening, and appeared not at all to
have suffered in its power of emitting light by the mixture and
confusion of its parts, so that it appears to depend more upon the
chemical nature of the substance than upoji the vital powers of
the animal ; but at the same time, it appears, from the variations
in splendor, accompanied by motions i7i the living animal, that it
may be much influenced or ^nodified by, or in some 7nanner
submitted to, the powers of the worm.

"The matter which appears to fill the hinder part of the
body in the shining season is yellowish-white, soft, and glutinous.
It is insoluble, apparently, in water or in alcohol. It does not
immediately lose its power of shining in water. Heat forces
out a bright glow, and then it becomes extinct ; but if not
carried too far, the addition of moisture after a time revives its
power. No motion or mixture seems to destroy its power
whilst it remains fresh and moist, but yet a portion thus rubbed
sooner lost its light than a portion left untouched. The time
of its continuance in a luminous state was very various, and
perhaps depends upon the state of the worms from which it
was taken. The death of the worm seemed to have no imme-
diate effect upon the illumination of the hinder part ; and with
respect to the length of time that it continued to shine after-
wards, it seemed indifferent whether it was left on the body or
taken off; but when extinct, exposure of the interior to air
always caused a fresh emanation of light. I found a worm
which emitted light from a very small part of the body, and
very feebly, and for a very short time together. The worm

BASIS OF ANIMAL PHOSPHORESCENCE. 1 05

was larger than the ordinary species, and had more divisions.
The power of emitting light in the ordinary worm seemed
proportionate to the age of the animal."

Monday, Ilth. " The matter of the worms referred to yes-
terday still shines. It was detached from the animal at 8.24,
and still promises to emit light much longer."

Tuesday, l2tJi. "The matter was luminous this day at
10.41, though faintly, and at twelve o'clock no light could
be perceived. The matter had become quite dry and semi-
transparent, but the addition of water produced no particular
effect."

Faraday's results may be briefly stated as follows : —

(i) There is a chemical substance in the glow-worm and the
fire-fly which has power to shine independently of the life of
the insect.

(2) This substance is probably a secretion of the insect.

(3) The shining depends on the respiration, and the air is
enough to cause this substance to shine.

(4) From the variation in the splendor of light, accompanied
by motions in the living animal, the animal, as a whole, has
in some way the control of the external manifestation of light.

Matteucci, also, in his letter to Duma,^ and elsewhere,^ came
to the same conclusion as Faraday, and says : '' In the glow-
worm there is a substance which, without any sensible heat,
diffuses a light that does not require the integrity of the
animal and of its living state in order to manifest itself with
its peculiar properties."

It will contribute to the clearness of the whole, if, instead of
examining various other theories proposed from time to time,
in the nature of animal light, I dwell briefly here on the rela-
tion of objective and subjective aspects of what we call the
sensation of light and of heat, or the relation of various kinds
of ether vibrations to the specific energy of senses.

We habitually associate the sensation of light with that of
heat, so that it becomes almost impossible to separate them in

1 Carlo Matteucci: Sur la phosphorescence du Lampyre d'ltalie (L. Italica).
CompL Rend. XVII, p. 309, August 14, 1843.

2 Matteucci : Lectures on the Physical Phenomena of Living Beings, 1848, p. 165.

I06 BIOLOGICAL LECTURES.

our common experience ; and when we meet with such a phe-
nomenon as the production of light from the animal tissue
without any sensible heat, it appears as if it were a totally
isolated physiological phenomenon with no parallel in the
ordinary activity of life.

According to the physicist, however, the external agent
which gives rise to the sensation of light in our organism is
not much different from that which gives rise to the sensation
of heat. Heat and light are only the variations of the same
radiant energy. There is an absolute continuity in the nature
of the two phenomena — the vibrations of ether.

"When the wave-length is greater than 812 millionths of a
millimeter no luminous effect is produced on the eye, though
the effect on the thermometer may be very great. When the
wave-length is 650 millionths of a millimeter the ray is visible
as a red light, and a considerable heating effect is observed.
But when the wave-length is 500 millionths of a millimeter, the
ray, which is seen as a brilliant green, has much less heating
effect than the dark or the red rays, and it is difficult to obtain
strong thermal effects with rays of smaller wave-lengths, even
when concentrated." ^

The light and heat are so very different to us because we
perceive them with different organs of sense. The heat radia-
tion, or the waves of ether which have most heating effect, we
perceive with the organ of temperature sense, while a similar
radiation, with different wave-lengths, which have most liLmi-
nous effect, we perceive with the organ of sight.

The difference between heat and light, therefore, " is purely
subjective, depending on our organization and not on the nature
of external objects." ^ There is an absolute continuity in the
nature of external disturbances which create in us the sensa-
tions of heat and of light, the difference between them being
that of degree and not of kind. Expressed, therefore, in terms
of visual sensation, heat is invisible light ; and light, expressed
in that of temperature sense, is heat with a very little heating
effect.

1 Clerk-Maxwell : Theory of Heat, Chap. XVI., On Radiation, p. 239.

2 Stokes: On Light, p. 266.

BASIS OF ANIMAL PHOSPHORESCENCE. 1 07

If our organs concerned in the sensation of light were some-
what different from what they are now, it is possible that what
appears as luminous may have no such effect, and what appears
as dark may even appear as luminous. *' It is quite conceivable
that animals might exist to which obscure heat rays might be
visible, and to which man and mammals generally would appear
constantly luminous." ^

The animal organism is an actual apparatus of combustion,
in which carbon compounds are constantly burnt, and from
which carbonic acid is always escaping. There is no difBculty
in conceiving that organisms which produce heat in this way
may under certain circumstances produce light, if the combus-
tion of the material in the body could be carried on in such a
manner as to impart a more rapid vibration to the surrounding
ether than that which results in the production of thermal
radiation.

The vibration of ether thus produced with higher frequency
and of shorter wave-lengths, such as we see in the fire-fly,
would affect the organ of vision, but not the organ of tempera-
ture. A7id this difference of result^ so conspicuous to tis, may not
imply 7nore than a very slight variation on the part of the indi-
vidual organism at the start. Nature desires, if I may use
such an expression, nothing but light in such an organism as
the fire-fly, and produces this with the least possible waste.

That this is a legitimate inference may be shown from the
several works of physicists. Several years ago Professor
Young 2 examined the spectrum of the fire-fly and stated his
important observations in the following form.

*' The spectrum given by the light of the commom fire-fly of
New Hampshire {Photinus ?) is perfectly continuous, without
trace of lines either bright or dark. It extends from a little
above Fraunhofer's line C in the scarlet to about F in the
blue, gradually fading at the extremities. It is noticeable
that precisely this portion of the spectrnm is composed of rays,
tvJiicJi^ while they more powerfnlly than any others affect the

1 Mosely: Notes by a Naturalist on H. M. S. Challenger, 1892, p. 512.

2 C. A. Young : Spectrum of the Fire-fly. Amer. Naturalist, Vol. Ill, 1870,
p. 615.

I08 BIOLOGICAL LECTURES.

organs of vision^ produce hardly any thermal or actinic effect. In
other words, very little of the e7iergy expended in the flash of
the firefly is wasted. It is quite different with our artificial
methods of illumination. In the case of an ordinary gaslight
the best experiments show that not more than one or two per
cent of the radiant energy consists of visible rays, the rest is
either invisible heat or actinism ; that is lo say, over ninety-
eight per cent of the gas is wasted in producing rays that do
not help in making objects visible."

Of Professor Langley and Mr. Very's more recent and well-
known paper *' On the Cheapest Form of Light," ^ most of you are
doubtless aware. As their observations are the most accurate
extant on the physical properties of animal light, it will not be
out of place to reproduce here at length the essential points of
their conclusions, as well as some of their instructive state-
ments on the concepts of radiant energy, which underly their
experimental inquiries.

"We recall," says Professor Langley, "that in all industrial
methods of producing light, there is involved an enormous
waste, greatest in sources of low temperature like the candle,
lamp, or even gas illumination where, as I have already shown, it
ordinarily exceeds ninety-nine parts in the one hundred ; and
least in sources of high temperature like the incandescent light
and electric arc, where yet it is still immense and amounts, even
under the most favorable conditions, to very much the larger
part" (p. 97).

" It is now universally admitted that wherever there is light,
there has been expenditure of heat in the production of radia-
tion existing in and as the luminosity itself, since both are but
forms of the same energy; but this visible radiant heat which
is inevitably necessary is not to be considered as waste. The
waste comes from the present necessity of expending a great
deal of heat in invisible forms before reaching even the slight-
est visible result, while each increase of the light represents not
only the small amount of heat directly concerned in the making

1 S. p. Langley and F. W. Very : On the Cheapest Form of Light, from Studies
at the Allegheny Observatory with Plates III, IV, and V. The American Journal
of Science, Third Series, Vol. XL, No. 236, August, 1890.

BASIS OF ANIMAL PHOSPHORESCENCE. 109

of the light itself, but a new indirect expenditure in the produc-
tion of invisible calorific rays. Our eyes recognize heat mainly
as it is conveyed in certain rapid ethereal vibrations associated
with high temperatures without passing through the interme-
diate low ones ; so that if the vocal production of a short atmos-
pheric vibration were subject to analogous conditions, a high
note could never be produced until we had passed through the
whole gamut, from the discontinuous sounds below the lowest
bass, up successively through every lower note of the scale till
the desired alto was reached.

"There are certain phenomena long investigated, yet little
understood, and grouped under the general name of ' phospho-
rescent,' which form an apparent exception to this rule, espe-
cially where nature employs them in the living organism, for it
seems very difficult to believe that the light of a fire-fly, .for
instance, is accompanied by a temperature of 2000° or more
Fahr., which is what we should have to produce to gain it by
our usual processes. That it is, however, not necessarily impos-
sible, we may infer from the fact that we can by a known physi-
cal process produce a still more brilliant light without sensible
heat, where we are yet sure that the temperature exceeds this.
No sensible heat accompanies the fire-fly's light any more than
need accompany that of the Geissler tube ; but this might be
the case in either instance, even though heat were there, owing
to its minute quantity, which seems to defy direct investigation.
It is VLSUdWy assumed With, apparent reason, that the insect's light
is produced without the invisible heat that accompanies our
ordinary processes, and this view is strengthened by study of
the fire-fly's spectrum, which has been frequently observed to
diminish more rapidly toward the red than that of ordinary
flames. Nevertheless this, though a highly probable and rea-
sonable assumption, remains assumption rather than proof, until
we can measure with a sufficiently delicate apparatus, the heat
which accompanies the light, and learn not only its quantity,
but what is more important, its quality " (pp. 98, 99).

Under *' Photometric Observations," the authors continue :
" The first impression in viewing the light of the Pyrophortis
noctilucus through a spectroscope is that it consists essentially

no BIOLOGICAL LECTURES.

of a broad band in the green and yellow, while with precaution
we see this extending into and beyond the borders of the blue
and orange, but not very greatly farther, and these have been
taken by previous observers as its absolute limits. No one
appears to have experimentally and distinctly answered the
question, " Would the light not extend farther were it bright
enough to be seen ? " nor has it been proved as clearly as
might be desired that the result depends on the quality rather
than the quantity of the light, or given conclusive evidence
that if the light of the insect were as bright as that of the
sun, it would not extend equally far on either side of the
spectrum.

" It is impossible to increase the intrinsic brilliancy by any
optical device, but if it be impossible to make the light of the
insect as bright as that of the sun, it is, on the other hand, quite
possible to make the light of the sun no brighter than that of
the insect, and this would appear to be the first step in obtain-
ing a definite proof that the apparently narrow limits of the
insect's spectrum are due to the intrinsic quality of the light,
and not to its feeble intensity. The only conclusive method of
determining this would appear to be to balance the light from
the insect with that of a definite portion of sunlight by any
ordinary photometric device ; and having taken this sunlight
as nearly equal as possible to that of the insect, though certainly
not greater, to let this determined quantity fall on the slit of
a spectroscope at the same time with the light from the insect,
two spectra being formed one over the other in the same field
and at the same time " (pp. 103, 104).

After detailing a number of experiments, the authors state
that *'when spectra are formed from two equal lights, one from
the sun, the other from the insect, the latter's spectrum termi-
nates both at an upper and a lower limit, at which the solar
light is still conspicuous. The conclusion follows that the
insect spectrum is lacking in rays of red luminosity, and pre-
sumably in the infra-red rays, usually of relatively great heat,
or that it seems probable that we have here light withotit heaty
other than that heat which the luminosity itself comprises and
which is but another name for the same energy" (p. 108).

BASIS OF ANhMAL PHOSPHORESCENCE. I I I

Under ''Thermal Observations" the authors proceed : "To
give an idea of the amount of heat at our disposition for experi-
ment, and of the actual minuteness of the radiation which pro-
ceeds from even the most luminous tropical insect, we may say
that if that rate of radiation from a lamp-black surface i square
cm. in area, which represents the amount of heat necessary to
raise i gram of water to i° centigrade, in i minute {i.e, one
small calorie), be taken as unity, then the luminous radiation of
the fire-fly's heat, per square cm., of exposed luminous surface,
as we have found, is about 0.0004 calorie in 10 seconds, and the
total luminous radiation from the most powerfully illuminating
light spot of the insect (the abdominal one) will not exceed
0.00007 calorie in the same time. But a small portion of this
could fall upon the bolometer, and that which actually reached
it during the time (10 seconds) required for each observation was
sufficient only to affect an ordinary mercurial thermometer
having a bulb i cm. in diameter by rather less than 0.00000023,
or by less than 1/400000 of one degree centigrade" (pp. 108,
109).

" Resuming, then, what we have said, we repeat that nature
produces this cheapest light at about one four-hundredth part
of the cost of the energy which is expended in the candle-flame,
and at but an insignificant fraction of the cost of the electric
light or the most economic light which has yet been devised ;
and that finally there seems to be no reason why we are for-
bidden to hope that we may yet discover a method (since such
a one certainly exists and is in use on a small scale) of obtain-
ing an enormously greater result than we now do from our
present ordinary means for producing light" (p. 112).

The light emitted by the living organism differs very much
in color in different animals, and even in the same animal at
different periods ; green has been noticed in the glow-worm,
fire-flies, some brittle-stars, centipedes, and annelids ; blue is
seen in the Italian fire-fly ; blue and light-green are the pre-
dominant colors exhibited by marine animals ; the beautiful Gir-
dle of Venus, some species of Salpa, and Cleodora appear red ;
Pavonaria and other gorgonids are lilac ; and one hemiptera, Ful-
gora, is said to emit a purple light. One very remarkable

112 BIOLOGICAL LECTURED.

Appendicularia showed in one individual first red^ then blue^
and finally green} This remarkable property seems to be pos-
sessed by other tunicates, for Huxley ^ states in his well-known
paper on Pyrosoma, quoting Peron, that Pyrosoma exhibited
movements of alternate contraction and dilatation at regular
intervals ; and that each contraction was accompanied by the
development of a luminosity, which, when at its brightest, was
red^ but in dying away passed through shades of orange, green,
and blue. Newport ^ also noticed a change in the color of light
emitted by the glow-worm at the end of the season from that
at the beginning. I have learned in the study of several species
of fire-flies, in the neighborhood of Woods Holl laboratory, to
distinguish them at a distance by the color of their light,
which, though slight, is still quite characteristic of the species.

The difference in color, when exhibited by different organ-
isms, is probably due to some slight chemical differences in the
light-giving substance. It may be supposed that under the
influence of oxygen, the molecules of the given photogenic sub-
stance are set in vibration, the rate of vibration depending on
and being characteristic of the particular species. And in those
cases where a series of colors are displayed in succession by the
one and the same organism, it may be supposed to be due to
either of two causes : (i) the same photogenic substance is agi-
tated with different degrees of frequencies at different periods
in the life of the organism, or (2) a series of photogenic sub-
stances are produced, each one of the series representing a stage
in the chemical metamorphosis of the substance. Without
some definite chemical knowledge on the nature of such photo-
genic substances, however, it is useless to make any conjecture
at present.

Nor is it easy to offer any plausible explanation as to the use
of such light to the organism, which will apply with equal force
to all cases. We may say this much, however, that if heat inci-

1 The above is taken from W. E. Hoyle's article Phosphorescence, in the
Encydopcedia Brittanica, Vol. XVIII, 1885.

2 Huxley : On the Anatomy and Development of Pyrosoma. Phil. Trans.,

1859.

8 Newport : On the Natural History of Glow-worms. Pi-oc. Lin. Soc, Vol. I,
1857.

BASIS OF ANIMAL PHOSPHORESCENCE. 113

dentally produced at first as a result of some necessary chemical
changes in the body may be utilized in the course of the race
history of an organism (as among birds which use heat evolved
by the metabolism of their tissue for the process of incubation),
it is equally conceivable that light incidentally produced as the
result of a necessary combustive process of life may eventually
be utilized in the race history of some species, and thus that
which is an end in one organism may become the means to a
remoter end in another organism. The mere fact that in some
animals the light is of no apparent use to them is no reason to
doubt that it may be of some use to others, in which the pro-
duction of light becomes the end and purpose of some definite
structure, and is even brought in connection with the mechanism
of the will.

While the production of light may be regarded as belonging
to the same ultimate cause as that of heat, the proximate cause
of the luminosity in the animal kingdom may be due to a variety
of secondary circumstances.

Thus (i) an organism may appear brilliant in the dark, owing
to the presence of luminous bacteria in the tissue.^ In such a
case, the luminosity of the organism may be considered as a
pathological phenomenon.

In another instance (2) the organism may appear luminous
also on account of the luminous bacteria which live in a sym-
biotic fashion in the tissue of the organism, but this cannot be
called a disease, as the animal suffers no bad consequence, and
may even be benefited by it.^

In still another case (3) transparent pelagic organisms like
some Crustacea may appear phosphorescent from containing in
their stomachs phosphorescent food, which shines through the
body of the organism. In a case like this their excrement is
also phosphorescent.^

1 See Giard : Sur I'infection phosphoresc. des Talitres et autres crustacees.
Compt. Rend.^ Sept. 23, 1889, p. 503. Peter Schmidt : On the Luminosity of
Midges {Chironomus). Zool. Jahrb. Abth. f. Syst. Geog. tmd Biologie, Bd. VIII,
Heft I, 1894. Ann. and Mag of Nat. Hist.., Vol. XV, 1895 (translated by Austen).

2 R. Dubois : Sur le role de la symbiose chez certains animaux marins lumineux
[Pelagia et Pholas]. Cotnpt. Rend., Tome CVII, 1888, p. 502.

3 H. N. Moseley: Notes of a Naturalist, p. 498.

114 BIOLOGICAL LECTURES.

In the truly phosphorescent organism the luminosity is
due to the metabolism of the definite tissue-cells, and the sub-
sequent oxidation of the metabolic product, which results in the
emission of light.

There can be no doubt that the majority of luminous
organisms belong to this type. In some, certain cells of
the body acquire the light-producing property at a certain
stage of development ; in others, the organisms are luminous
from the beginning of their life history. Thus Alexander
Agassiz 1 observes ** that the phosphorescence is equally brilliant
in the ^^g of Ctenophorae as in the adults, even in stages in
which the masses of segmentation can still be counted. The
whole embryonic mass becomes brilliantly phosphorescent when
the least shock is given to the jar in which the eggs are kept."

Dubois ^ also states that in Lampyris noctihcca the ova taken
from the ovaries and carefully washed after removal were still
luminous, the development of the light being in direct relation
with the degree of intraovarian development of the ova. The
photogenic power in such an ^^%y as in many luminous proto-
zoa, is exercised without the aid of trachea, nerves, or special
anatomical elements, showing that while these elements may
facilitate and even enhance for the time being the effect of
luminosity, they are not to be considered thereby essential to
the process of light production.

Phosphorescence is best seen in the ordinary fire-fly. If
you examine the luminous cell of the common fire-fly {Pho-
tmis pennsylvanicd), you will find it filled with peculiar yel-
lowish-white granules, the whole cell reminding one of some
actively secreting gland. These granules, by combining with
oxygen brought in through the trachea and tracheal ''capil-
laries," which closely invest the cells from all sides, give out
light. It is a process of combustion which, instead of giving
out heat, gives out light. These granules are the products of
metabolism, the result of '' secretion " process, due to the

. 1 A. Agassiz : Embryology of the Ctenophorae. Mem. Amer. Acad, of Arts
and Sciences, Vol. X, No. IV. Cambridge, Mass., 1874.

2 R. Dubois : De la fonction photogenique dans les oeufs du lampyre. Bull.
Soc. Zool. France, XII, 1887, p. 137.

BASIS OF ANIMAL PHOSPHORESCENCE. II5

decomposition of the living substance of the cell ; but instead
of being thrown out of the body, like some other products of
secretion, they are consumed in situ by combining with oxygen
brought in from without.

The fact that the granules themselves are dead is shown by
taking the luminous organ from the organism and crushing it
on the slide, thus depriving it of all traces of vitality ; yet the
light continues to come out, in fact it becomes more luminous
the greater the exposure to air.

The mode by which each luminous cell is aerated by the
tracheal '* capillaries " is of considerable interest. The "capil-
laries" are the ultimate branches of the respiratory apparatus,
and start from the ultimate branches of the tracheal tube, some-
what in a similar manner as the tentacles do from the body of
a hydra. If one imagines these " capillaries " are spread around
the photogenic cell in the same manner as the hydra spreads its
tentacles around an organism much larger than itself, which it
has captured for food, he may get a fair idea of the relation of
the aerating apparatus to the light-producing cell.

The size of the luminous cell being comparatively large, more
than one bunch of hydriform "capillaries" is found distributed
over the surface of each luminous cell. The substance of the
"capillaries" seems to have a remarkable affinity for oxygen,
and it is, no doubt, through this mechanism that the oxygen of
the inspired air is quickly separated, and just as quickly applied
for the combustion of the photogenic material in the periphery
of the cell.

As to the chemical nature of this material little is known ;
but it is a secretion of fatty nature, which oxidizes readily in
alkaline media. Phosphorus has nothing to do with the
phenomenon.

The animal has control of the production of light through
its respiratory mechanism, not directly upon the luminous
cell, although nerves may have indirect influence upon the
general metabolism of the cell. When more oxygen is sent
with the air, the illumination is greater ; when the air is with-
held, there is less light, or even a complete darkness, just as the
dull red coal may be ignited so as to emit a white light by a

Il6 BIOLOGICAL LECTURES.

Steady application of fresh air upon it by the action of the
bellows.

The fact that the illumination of the cell is due to the action
of oxygen may. be shown in a simple way by putting the slide
on which the luminous organ has been crushed, and the photo-
genic material spread out, into a jar containing carbon dioxide.
The light disappears almost instantly; but if the same slide be
placed in a jar containing oxygen, or simply exposed to air, the
light comes back, and lasts as long as the luminous material,
a certain amount of moisture, and other necessary conditions
are present.

This process can be repeated several times, showing conclu-
sively that the light-giving material itself is quite independent
of cell-life, although it owes its existence primarily to the life
activity of the cell as a whole.

The luminous phenomenon, wherever it occurs, is apparently
carried on by essentially the same process throughout the
animal kingdom. In air-breathing organisms, such as the
fire-fly, the product of cell metabolism is oxidized in sitti by
the oxygen of the inspired air. In some marine organisms the
secretion is often thrown out in the form of liquid from the
gland to the surrounding medium, and the oxidation is accom-
plished by the oxygen dissolved in the sea water. In luminous
Salpa the photogenic granules formed in the blood-corpuscles
are oxidized by the oxygen dissolved in the blood plasma.

Perhaps I can summarize the preceding, and make my point
more intelligible by the help of a diagram.

We have seen that the essential bases for the luminous
phenomena of the living organism consist (i) in the production
of a certain chemical substance in the cell, which recalls to our
mind the well-known series of phenomena in the process of
secretion ; and (2) the oxidation of this substance by the
oxygen brought in from without, and thus making the cell a
new center of disturbance to the surrounding ether.

BASIS OF ANIMAL PHOSPHORESCENCE.

M

117

Living Constituents of the Cell.

M Protoplasm

( (a) Cytoplasm.

NoN-LiviNG Constituents of the Cell.

(a) Food {A).

(b) Photogenic granules (Z).

I (b) Chromosome.
O Oxygen, acting on the photogenic

granules.
Z Light, emanating from the cell, as

the result of oxidation.

The food-substance, which I represent, for the sake of con-
venience, by the block {A) in the accompanying diagram, enters
the cell boundary, and becomes eventually assimilated into the
protoplasm (M) ; the complex living substance, or protoplasm,
becomes disintegrated into a number of granules {Z) which
are no longer ''living," and which may be regarded as refuse
of life. The definite chemical molecules which constitute
these granules combine with oxygen (0, and the molecular
agitation, which accompanies the chemical process of combus-
tion, sets the surrounding ether into a state of vibration (Z),
which has a powerful luminous effect on us, but little or no
thermal effect.

Thus, the life of the luminous cell, like that of any other
cell, begins with the physical and ends with the physical. We
know the beginning {A)\ and we also know the termination (Z).
The unknown territory in the middle {M) is what we call the
protoplasm, or the matter in the living state.

Il8 BIOLOGICAL LECTURES.

There is one suggestion of some importance which flows
from this.

That most Hving matter needs oxygen for the maintenance
of life is a well-established fact, but in what precise manner
this oxygen is ultimately used in the organism, is a question to
which we can give hardly any satisfactory answer at present.

In the luminous cell of the fire-fly, in which the mechanism
of oxygenation is carried to its highest perfection, it is com-
paratively easy to trace the path of oxygen, and how it is used
in the living cell. TJie oxygen here simply combines with tJie
dead substance prepared in the cell. The value of oxygen to the
luminous function of the organism lies in its ability to combine
with the dead substance produced by the activity of the living.
Is it possible that the relation of oxygen to life in general is of
a similar nature } Does the value of oxygen to life lie primarily
in its ability to combine with the dead substances, which exist
side by side with the living, in all cells } The haemoglobin is
a complex iron compound found in the red blood-corpuscle.
Oxygen loosely combines with this compound and forms oxy-
haemoglobin. The oxygen in this new compound is given up
in the tissue through which the blood circulates, and the com-
pound returns back to the original haemoglobin, which, coming
back to the respiratory organ, combines again with the free oxy-
gen, and begins the role of oxygen-carrier again. Here, again,
the substance in the cell which combines with the oxygen is not
the living substance, but the dead material formed by the activity
of the cell. Professor Loeb suggests that it is possible that
the relation of oxygen to life may be of this nature in all cases.

It may be that in the luminous cell of the fire-fly the method
of oxidation is carried out with a highly specialized apparatus,
and the result of oxidation of the dead material conveyed in
such a form as to affect the most delicate of our sense-organs,
and that the relation of oxygen to the life of the cell in gen-
eral is thus revealed here with simplicity and clearness unparal-
leled in the whole series of vital activities. At any rate, this
aspect of the question may not be devoid of interest when taken
in connection with the fundamental problem of the relation of
oxygen to living substance, or respiration, in which, some have
even maintained, lies hidden the whole mystery of life.

EIGHTH LECTURE.

THE PRIMARY SEGMENTATION OF THE VERTE-
BRATE HEAD.

WILLIAM A. LOCY.

(Lake Forest, III.)

The vertebrate head is the most complex piece of animal
architecture with which anatomists have to deal. It has been
produced by gradual modifications of a simpler basis, and dif-
ferentiation has been carried farther in it than in any other
part of the animal. It represents, therefore, the widest depar-
ture from archetypal conditions.

Its complex structure is correlated with the highest grade of
functions. The cranial sense-organs and the brain exhibit
the highest manifestations of vital activity to be found in the
whole range of living structures. The cranial sense-organs
serve to bring the organism into relation with the external
world, and the brain, besides being concerned with perception
and general mental life, contains nerve-centers for the coordina-
tion of the vital actions of the body. The structure and de-
velopment of the vertebrate head is therefore a topic of unusual
interest and importance in comparative anatomy.

In their efforts to understand the head, morphologists
and physiologists have made use of every available means of
research ; observations on the minute structure have been
supplemented by studies in embryological development and
physiological experimentation. The whole work has been
carried on from the standpoint of comparative anatomy. The
results have not been just what might have been expected
They have not led to the solution of the fundamental questions,
but have served rather to open the field and reveal its extent

I20 BIOLOGICAL LECTURES.

and complicated nature. A research once begun leads out in
all directions into the unknown, and a crop of new problems
springs up in the path of the original investigator. It is en-
couraging to biologists to know that every research serves
to enlarge the field of their activity ; the conquered territory
affords points of vantage from which the horizon is enlarged.
Thus the work of morphologists and physiologists on the
head, although not giving a complete solution to the problems
undertaken, has brought us larger views and more interesting
and suggestive lines of inquiry.

Out of the great group of subjects connected with the
morphology of the head, I have chosen one that relates to the
primitive segmented condition. If we propound the question,
What was the rudimentary condition of the vertebrate head.?
we shall find it may be partly answered in the light of modern
research as follows : It was originally composed of a series of
similar segments that were structurally like those that compose
the trunk. A mental picture of this rudimentary condition
may be formed by thinking of the broad cephalic plate (or
rudimentary head) of very early embryonic stages as divided
by transverse constrictions into ridges and furrows that pass
backward from the head into the trunk, and give the whole
embryo a jointed structure similar to that of an articulated
animal. The segments or folds do not cross the median plane,
and are therefore in pairs. From this simple condition the
complex head has arisen by differentiation and specialization.
It follows, of course, that the distinction between head-region
and trunk-region is one of degree of differentiation and not of
kind.

The head is least modified in the youngest embryos, and if
we begin our observations with the earliest stages its trans-
formations may be traced by observing successively older
embryos. The modifications which the head has undergone
have been brought about gradually, and are so comprehensive
in their range that if we could know their complete history,
even in one animal, we should have a key to the leading ques-
tions of vertebrate descent. But there are so many causes
tending to modify the course of development, that we cannot

THE PRIMARY SEGMENTATION. 121

depend on the steps of ancestral history being repeated in a
complete and orderly way in any animal form, and our observa-
tions give us only circumstantial evidence from which a balance
of probabilities must be struck to determine what is ancestral
and what is secondarily acquired. The chain of evidence is
incomplete, and must always be supplemented by a certain
amount of inference, but it has not been fully recognized in
the practical study of embryological development that the
shortest intervals of time may be very important in keeping
the connection. Coherency of history must be preserved.
The difficulty of doing so is greatly increased by the fact that
the new is made to proceed out of the old, and frequently one
organ insidiously takes the place of an earlier formed one. I
am glad of the opportunity to say, in this company of investi-
gators and students who are preparing for independent research
in biology, that too great stress cannot be laid on the desir-
ability of having a more complete series of stages for study.
The traditional method has been to study one stage, and then
another '*a little older," and fill in the gap with inferences.
This has proved to be inadequate and misleading. It is now
required that we shall have stages near enough to trace the
history of the transitory as well as the permanent organs ;
embryologists are just beginning to realize how transitory
some organs are. I have recently had occasion to examine a
set of embryonic structures in the chick, which do not appar-
ently last more than an hour or two in the course of develop-
ment, but which are, nevertheless, clearly defined for that
period and then fade away. In this particular case the agree-
ment of two observers, even as to the presence of these organs,
would depend on their having stages of identically, not approxi-
mately, the same period of development. A wider recognition
of the existence of such conditions would give us fewer contro-
versies and less biological mythology.

Above, it was stated that the vertebrate head is primitively
segmented, and it is manifestly an interesting problem to deter-
mine the number, the nature, and the transformations of the
segments that have entered into the composition of the head.
The individual segments are called metameres, or somites, and

122 BIOLOGICAL LECTURES.

the jointed condition is designated "metamerism of the head."
Under that title the question has recently received much atten-
tion. It is not a new question, having been started at the
beginning of this century, but there has been a revived interest
in it on account of new discoveries. It was the most promi-
nently discussed question before the Anatomical Society of
Germany, at their meeting in Vienna, in 1892. There were
important papers on the subject by some of the foremost
anatomists, — Froriep, Kupffer, Hatscheck, Rabl, Killian, — all
followed by discussion, and the question of metamerism of the
head received there a consideration worthy of its importance.
There have been new developments since that time, tending to
modify some of the conclusions reached in that learned body,
and the subject is, on account of its freshness, a particularly
good one to present here.

The presence in the head of such segmental structures as
cranial nerves, branchial clefts, of the adult and embryonic
stages, the so-called head cavities and neural segments, have
been sufficient evidence to support the general proposition that
the vertebrate head is segmented in its unmodified condition.
But there has been no agreement as to the number, nature,
or transformations of these segments, nor as to their anterior
limit. In fact, the fore-brain has generally been regarded as
not included in the segmented area.

Segmental folds have been observed in the hind-brain of
embryos of different animals since 1828, so there has been no
question as to the segmented condition of the posterior part of
the brain, but, so far as the evidence (except the very latest)
goes, the segments seem to vanish in the region of the fore-
brain, and the general interpretation has been that the fore-
brain is non-metameric. The two anterior pairs of nerves com-
ing from the fore-brain — olfactory and optic — have also until
very recently been placed, by common consent, in a different
category from the other cranial nerves. Moreover, the head has
been considered, by some of the most careful students of our
time, to be derived from an unsegmented ancestral rudiment
found in an enigmatical larval form of the annelids. All this
gave rise to the assumption that the brain of invertebrates and

THE PRIMARY SEGMENTATION. 123

vertebrates contained an unsegmented anterior part, and the
question, How far forward does the segmentation extend ?
is a very important one.

The evidence to elucidate this point has been accumulating,
and I think we are now in a position to answer that fundamen-
tal question. Already the olfactory nerves have been shown
to have a similar history to the cranial nerves, and, to all
appearances, the optic nerves are soon to be included with the
others. The Director of this laboratory has recently shown
conclusively that the head of annelids is metameric throughout.
The cerebral ganglion or brain of these animals is segmented
in the same manner as the ventral nerve-cord, and consequently
there is no non-metameric part of the nervous system, as has
been so long assumed. This must necessarily change the views
regarding the ancestral derivation of the vertebrate head.
Waters, Zimmerman, and others have shown the existence of
segments in the fore-brain of vertebrates, and further evidence
on that point will be brought out in this lecture.

The recent endeavors to solve the problem of metamerism
of the head are based on observations on cranial nerves and
branchial clefts, mesoblastic head cavities and neural segments.
These are the cephalic structures that exhibit segmental ar-
rangement, and we must depend upon them for evidence. It
is an open question to which of these the most importance is
to be attached. The first-mentioned basis, namely, cranial
nerves and branchial clefts, is the least favorable, as it involves
too much conjecture. Dr. Strong, of Columbia University, has
shown that the cranial nerves do not appear in the positions
they come to occupy, and McClure has stated the case against
the cranial nerves as follows : **We have positive proof that
the degeneration of certain branches has taken place. This
being the case, we have every reason to assume that whole
segmental nerves may have once existed, which have completely
degenerated, leaving no trace whatever of their previous exist-
ence. If such be the case, the segments originally connected
with these degenerated nerves must necessarily be overlooked,
if the existing nerves are made use of as a means of determin-
ing the original number of segments.

124 BIOLOGICAL LECTURES.

"■ Furthermore, the vagrant changes in the position of some
of the cranial nerves must necessarily cause confusion. For
example, take the sixth nerve, which in the frog and tadpole
stages is situated between the first and second roots of the
ninth nerve (given on the authority of Dr. Strong), a position
somewhat posterior to its place of origin. This remarkable
shifting clearly shows not only what great changes in position
the cranial nerves are capable of undergoing, but it also goes
to prove that we can find no reliable means of determining the
primitive segments by means of their connection with the exit
of the existing cranial nerves. Beard, in taking up this problem,
made use of an important series of sense-organs for which he
proposed the name ' branchial sense-organs,' from their de-
velopment from thickenings of the epiblast over each branchial
cleft. The dorsal branches of certain cranial nerves fuse with
these epiblastic thickenings ; the superficial part of the thicken-
ing gives rise to a branchial sense-organ, while the deeper por-
tion becomes the ganglion of the dorsal root of the cranial
nerve. This close relation which exists between the dorsal
branches of the cranial nerves and their corresponding sense-
organs is undoubtedly of segmental character. But this line of
research is beset by a great difficulty, namely, that the degen-
eration of certain sense-organs would, in time, involve the
degeneration of their corresponding cranial nerves, and such
degeneration has taken place, in part or in whole, leaving in
doubt the primitive segments with which they were connected."

The mesoblastic head-cavities and neural segments are both
more important clues to the metamerism of the head. The
mesoblastic head-cavities are called myotomes, and embody
the muscle rudiments, while the neural segments represent the
joints of the nervous system. Muscle and nerve are, physio-
logically, so fundamentally related that we should naturally ex-
pect some close correspondence between muscle segments and
neural segments, and metamerism of the head should be studied
in the light of observations on both sets of structures.

Balfour first studied the segmental divisions of the meso-
blast in the head of elasmobranch fishes, and, in 1874, identi-
fied by this means eight head somites. He also expressed the

THE PRIMA R Y SEGMENT A TION. \ 2 5

conviction that there were primitively a larger number of seg-
ments, but, owing to extreme modifications of the head-region,
they are no longer clearly represented.

From this time onwards, the myotomes became a great
favorite with morphologists in elucidating the problem of head
segmentation. They seemed, so far as the evidence went, to
embody the most direct survivals of the original segmentation,
and therefore to be the most promising line along which to
work out the problem. Van Wijhe's researches, published
about 1882, have been taken as the standard ones for reference ;
he identified nine head somites moulded in the mesoblast of the
head. This line of investigation received a great stimulus in
1890, from the work of Dohrn, who discovered eighteen or
nineteen myotomes in the head of torpedo embryos. In 1892
Killian substantiated his discoveries and reduced the enumer-
ation by one. It appears, therefore, that there is a larger
number of head somites than was at first supposed.

The neural segments are comparatively recent in their claims
to attention as bearing evidence to the original segmentation
of the head, and their importance in this connection has not
been fully appreciated. Their early history has recently been
made known, ^ and this shows them in a new light. The neural
segments are the first to appear, and are less subject to modi-
fications in the early stages than the muscle segments of the
head. The large number of myotomes described by Dohrn
and Killian are transitory, and after a very brief existence they
become reduced by fusion, or absorption, or both, to the nine
head-cavities of Van Wijhe. But the neural segments make
their appearance very early and preserve their original number
and characteristics for a considerably longer period. It has
been assumed that the muscle segments are primary and that
the neural segments are secondarily moulded over them ; but, as
we shall see, this position cannot be sustained in the light of
recent observations, and it is timely to ask which set of seg-
mental structures affords the most reliable evidence as to the
primitive number of brain segments.

1 Locy : Metameric Segmentation in Medullary Folds and Embryonic Rim.
Anat. Anz., Bd. IX, No. 13, 1894 ; 2i\so Journ. Morph., Vol. XI, No. 3.

126 BIOLOGICAL LECTURES.

I have said that the metamerism of the head should be in-
vestigated in the light of work done on both myotomes and
neural segments, but here I can present only one side. The
case for the myotomes has been so completely presented by
Dohrn, Killian, and others that I waive a consideration of that
side of the question, and dwell on the history of the neural seg-
ments and speak of the new observations on them.

The neural segments were observed in the hind-brain of
embryo chicks by Von Baer as long ago as 1828. They have
been observed and commented upon by many anatomists since
that time. In 1850 Dursy made the important suggestion
that the neural segments are genetically related to the cranial
nerves, but he had no direct evidence of this. To Beraneck
belongs the credit of having first demonstrated, in 1884, that
there is a definite relation between neural segments and certain
cranial nerves. This was the first substantial basis towards
establishing their segmental importance. Orr, 'Zj, McClure,
'90, and Waters, '92, followed this pioneer work, demonstrating
the definite relation^ of the nerves of the hind-brain to specific
neuromeres. McClure showed also that the entire neural tube
is divided into similar segments, and Waters gave particular
attention to the fore- and mid-brain. He found in the lizard
evidence of three somites in the fore-brain, making a total of
eleven somites in the entire brain-region.

In Europe Froriep, Kupffer, Rabl, Hoffmann, Zimmerman,
and others have made recent contributions to the knowledge
of these neural segments. In 1892 Froriep described anew
the neural segments and attached no particular importance to
them. He expressed the conclusion that the neural segments
are secondarily moulded over the segmental divisions of the
mesoblast. The latter, in common with most other writers, he
regards as primary. I hope to show you before the conclusion
of this lecture that the position cannot be sustained.

Let us now see what may be learned regarding the primitive
segments of the head by the examination of young embryos.

1 1 prefer to omit in this general lecture the question of the relationship of par-
ticular cranial nerves to particular neural segments, which is of so great interest
and importance to the morphologist.

THE PRIMARY SEGMENTATION.

127

In choosing an advantageous animal for observation, we should
take a vertebrate that has undergone relatively few modifica-
tions. Of course, any living animal is very far removed from
the ancestral type, but we should expect to find the closest
approach to ancestral conditions in the simplest ones. The
sharks present many generalized features and we may as well
begin with them.

It is to be understood that I am responsible for the observa-
tions that follow, as they have not, as yet, been substantiated
by any other observer. The careful examination of an elasmo-
branch embryo in an early stage of development shows the
existence of segmental folds that extend from the extreme

Fig. I. — Very young embryo of Acanthias showing primitive segments.

anterior end to the posterior limit of the embryo. Fig. i
represents such an embryo. The specimen from which the
sketch was made had attained a length of i.i mm. The
axial part of the embryo is established ; its anterior end is
rounded and slightly broader than the rest of the embryo.
There are eight pairs of segments in the axial embryo, and
they extend beyond into the blastodermic rim. If these seg-
mental folds occurred only in isolated cases, or in a single
embryonic stage, we should attach no especial significance to
them, but they are present in all normal specimens, and their
history shows their segmental importance. Once established,
they may be traced onwards in unbroken continuity and finally
identified with the neuromeres described by Orr, McClure, and
others. There are three or four pairs of mesoblastic divisions
in this stage that occupy a limited area in the narrow part of

128 BIOLOGICAL LECTURES.

the embryo, but the segmental folds are comprehensive in ex-
tent and cannot depend on these few proto vertebrae.

The examination of a slightly older embryo, Fig. 2, gives a

Fig. 2. — Young embryo of Acanthias showing primitive segments. Those numbered i-ii lie in
front of the point of origin of the vagus nerve.

similar picture. The segments are a little better developed,
and the broad head-region is roughly marked off from the more
slender trunk-region. The segments extend along the margin
in pairs. As in the former case, they extend beyond the limit
of the axial embryo into the embryonic rim. There are eleven
pairs in the broadly expanded head end. It may be determined
by tracing them into later stages that the eleventh neuromere
is just in front of the place of origin of the front root of the
vagus nerve.

It is obvious that this young animal that is to be hatched
from the ^g^ as a vertebrate is now an invertebrate. It ex-
hibits an arthromeric condition similar to that in animals of the
articulated group. The segments, although faintly expressed,
are definite in number and arrangement, and the inference to
be drawn from their presence is clear. As Dr. Whitman has
said : " This is a stage through which every vertebrate passes
on its way from the ^gg to the adult, a stage in which the fish,
the amphibian, the reptile, the bird, the beast, and man find
a common level, and in which every title to superior rank
lies in unexpressed potentialities. But more than this ; for
it is here that the vertebrate is an invertebrate and stands
beside its prototype, the segmented worm. On the same

THE PRIMARY SEGMENTATION,

129

metropolitan plane the lobster, the crab, the insect, in short
all the members of the great arthropod group, meet and
acknowledge their community of descent. Thus the great
branches of the genealogical tree represented in the larger
types first defined by Cuvier converge and meet in a common
trunk which bears the deep and enduring mark of metamerism."

Fig. 3. — Older embryo showing metameric segments in the head-plate. The neural folds of the head
are nearly in the horizontal plane, op, beginning of the optic vesicle.

Fig. 3 shows an older embryo with a slender trunk and
broadly expanded head. The optic vesicles {op) have made
their appearance on the head-plate. The neural segments are
well shown on the left-hand margin of the cephalic plate.

Fig. 4 shows a still older embryo in which the neural folds
of the head have grown upwards to form an open neural groove.

Fig. 4. — Embryo with open neural groove,
vesicle, he, head-cavity.

1-13 metameres of the neural folds. oP, primary optic

130 BIOLOGICAL LECTURES.

The embryo is viewed obliquely from the right side. The rudi-
ments of several organs — optic vesicles, branchial pouch, etc.
— have appeared upon the lateral walls of the head. Direct-
ing our attention to the margin of the nearest neural fold, we
note that it is clearly segmented throughout the head-region,
and backwards into the trunk to the point where, in the figure,
it disappears behind the yolk. The metameres extend, in
reality, to the posterior limit of the body.

The next stage to be considered. Fig. 5, is immediately after

^^ <^ /^ /-o «

jf

'op

Fig. 5. — Head of embryo of Acanthias after closure of the neural groove but before the formation
of the auditory vesicle. Reference marks as in the previous figure.

the closure of the neural groove and before the auditory vesicle
has made its appearance. Certain anatomical landmarks of the
head-region have become established, and it is now possible to
determine the relation of the neural segments to other cephalic
structures.

It is to be noted that the metameres of the fore- and mid-
brain are still visible from surface views, and almost immedi-
ately become indistinguishable in these regions, but continue
to be well defined in the hind-brain. There are five segments
well shown in the combined fore- and mid-brains. Three of
these probably belong to the fore-brain and two to the mid-
brain. All the embryos so far described exhibit the segmental
folds to the anterior end of the head, and a definite answer is
returned by these observations to the fundamental question
already proposed : How far forward does the segmentation
extend.? In view of the facts, we are justified in concluding

THE PRIMARY SEGMENTATION.

131

that the extreme anterior end of the vertebrate brain still bears
the marks of primitive segmentation. This, as Dr. Whitman
has shown, is also the case with the invertebrates.

In Fig. 6, the auditory vesicle is formed. The neural seg-
ments of the fore- and mid-brains are no longer discernible

'mb

Fig. 6. — Head of embryo after the formation of the auditory vesicle, the first five head segments no
longer distinguishable, au, auditory vesicle, na, nasal epithelium, tnb, mid-brain.

from surface view, but those of the hind-brain, beginning with
No. 6, are clearly seen. The neuromeres of that region are
now in contact in the median plane ; soon, by the lateral growth
of the upper brain wall, they become separated as shown in Fig.
7. This is the stage in which neural segments have been here-
tofore described. They have been designated neuromeres. The

Fig. 7. — Head of embryo somewhat older than the one in Fig. 6.
Other reference marks as before.

nv, beginning of the fifth nerve.

132

BIOLOGICAL LECTURES.

cranial nerves have begun to develop and show definite relations
with some of the neuromeres of the hind-brain. For example,
as is best shown in Fig. 7, the fifth nerve is connected with the
first and second neuromeres of the hind-brain, that is, with the
segments Nos. 6 and 7. The eighth neuromere has no nerve
connection ; the seventh and eighth
nerves are connected with the ninth
and tenth neuromeres ; the ninth nerve
with the eleventh neuromere, and the
front root of the vagus is connected
with the twelfth segment.

The evidence of a primitive head
segmentation, which is so well preserved
in these animals, is by no means ex-
ceptional, as may be determined by
examining the embryos of other animals.
They are present at least in corre-
spondingly young stages of birds and
amphibia, and this considerable range
indicates they are a fundamental char-
acteristic.

In the very young chick, I have
repeatedly examined them in living
specimens. They are to be faintly
seen as early as the twelfth to the
fifteenth hour of incubation ; and from
that time onwards they are ever present
till they are obliterated by transforma-
tions in the brain. In the earlier
stages in which I have observed them
there are only three pairs, and they
apparently increase in number by backward growth. Fig. 8
shows the appearance of these segments in a chick embryo
while the neural groove is open. The segments extend from
the anterior limit of the head as far back as the neural folds are
established ; there are here four protovertebrae, but lying in
front of them and entirely distinct from them are eleven pairs
of the primitive neural segments.

Fig

8. — Embryo of chick, with
open neural groove and three
well-marked mesoblastic so-
mites. The neural folds are
segmented throughout their
extent.

THE PRIMARY SEGMENTATION. 133

These segments have also been studied in living embryos of
several amphibia in stages with an open neural groove. They
have also been identified in the early stages of the newt, the
frog, and the torpedo.

The neural segments have now been shown to occur in the
very early stages of a number of animals. The fact of their
presence in these early stages once established, they assume
new importance. They have a too definite history to admit of
being set aside as mere headings or undulations of no meta-
meric significance. The fact has to be confronted that these
neural segments are the early stages of the neuromeres, whose
characteristics have been determined by a number of observers.
So long as the neuromeres are supposed to be moulded over
the mesoblastic somites, they can have no particular importance
in the problem of head segmentation, but that view of the
neuromeres is an assumption made without a knowledge of
their early history. This early history, now made known,
places them in a new light, and, taken all together, the neural
segments furnish, I think, a more satisfactory basis for inter-
pretation of metamerism of the head than we have had before.

There is one question regarding the validity of these seg-
ments that must be disposed of before we can proceed further.
All investigators know that appearances simulating regular
structures may be produced by the reagents used in prepar-
ing material for study ; and the question comes to us. Are not
these segments artifacts produced by the action of chemicals }
Too great precaution cannot be taken in sifting this matter to
the bottom. The large number of specimens studied as a basis
for the facts already given were prepared by a variety of
methods. They were treated with reagents well known to
morphologists, such as picro-sulphuric acid, picro-nitric, Flem
ming's solution, Davidoff's corrosive-acetic, chromic acid with
a trace of osmic, corrosive sublimate removed with iodine ; and
in all cases the segments have been distinguishable, not in
patches but in such condition as to admit of being counted,
and there has been uniformly the same number of segments
in the head-region. It is not reasonable to assume that the
different reagents would all produce the same effect.

134 BIOLOGICAL LECTURES.

The history of these segments, in Acanthias and the chick,
has been followed very carefully, and the earliest formed ones
have been traced without a break into later stages and identi-
fied with the neuromeres. If, therefore, the segments of the
open neural groove stage are artifacts, it may with equal force
be claimed that the so-called neuromeres, which are their later
stages, are also artificially produced.

It should also be borne in mind that similar segments exist
in correspondingly early stages in Amblystoma, Rana palustris,
the newt, and the chick, which indicates that they are not con-
fined to isolated cases but are a fundamental feature of verte-
brate development.

The most satisfactory indication of their true nature is found
by observing living material before it has been brought into
contact with any reagent. Fortunately, the chick offers at
all times a source where we can get living embryonic material
of any desired age. These segments have been repeatedly
observed in living chick embryos of the eighteenth to twenty-
second hour of incubation, and have been treated with re-
agents while they were actually under observation. The effect
of the addition of picro-sulphuric acid is to render, immediately,
the walls of the neural groove opaque and more clearly defined,
but not to affect the number or arrangement of the segments.
The same segments have also been studied in living embryos
of Amblystoma. These facts are conclusive ; if the segments
exist in living embryos, they are veritable anatomical structures.

Two points of fundamental importance may now be regarded
as established : (i) that the neural segments are present in
extremely early stages of vertebrates where they have not
heretofore been recognized, and (2) that they are true anatomi-
cal structures and not artifacts. The question still remains.
Do they furnish the best or even a good clue to the number of
segments in the primitive brain "^ If so, they must be shown
to be equally important in this direction with myotomes, bran-
chiae, and cranial nerves.

In estimating the claims of these various forms of segmental
divisions to rank as the primitive, the time of their respective
appearance in the developmental history will be significant.

THE PRIMARY SEGMENTATION. I 35

On this point I wish to observe that in all the forms studied,
embracing representatives of birds, amphibia, and selachians,
the neural segments are among the first anatomical structures
to be established ; before the vestiges of any organs have ap-
peared, the embryo is divided throughout its length into similar
segments. These metameric divisions, therefore, antedate
myotomes, branchiae, cranial nerves, or any other structures
that exhibit metamerism. They persist through the early
stages of development, and become definitely related to seg-
mental nerves and segmental sense-organs. In the light of
their early appearance and their history, I think we are justi-
fied in saying they are the most satisfactory traces of primitive
metamerism that are preserved in the group of vertebrates.

It should also be observed that the entire embryo is seg-
mented, and the term "metamerism of the head" should be
understood to signify merely regional metamerism, and not a
different kind of segmental division from that occurring in the
rest of the embryo.

The next point to be noted with regard to these segments
is that they are formed independently of mesodermic influence.
I have shown that the neural segments appear much earlier
than those of the mesoderm, and that they extend throughout
the embryo ; when, however, the protovertebrae appear they
are localized, and are formed backwards and forwards from the
point of their first appearance. But the final appeal must be
made to sections. A careful study of sections of shark and
chick embryos shows that the mesoblast is not divided into
protovertebrae in the head, even after that region is completely
segmented. In the sharks also, the neural folds that are so
evidently segmented, are at first wing-like expansions from
the body, and during this stage no mesoblast enters into them.
Therefore, the neural segments cannot depend upon the seg-
mental folds in the mesoblast. The combined facts place the
neural segments on a good basis for independent consideration
as survivals of primitive segmentation.

If the brain walls are completely exposed by removing the
overlying tissues, we may count the number of neural seg-
ments with complete satisfaction. In the brain of shark em-

136 BIOLOGICAL LECTURES.

bryos there are fourteen pairs of segments and an anterior
unsegmented tip that may represent a single pair or several
consolidated pairs. This is a larger number of neural seg-
ments than has heretofore been counted for vertebrate animals.
It approaches more nearly the number of head myotomes as
determined by Dohrn and Killian.

Finally, we are to conclude from a study of the neural seg-
ments that the vertebrate brain is primitively segmented to
its anterior tip ; that its segments do not, at first, differ from
those of the trunk, — in other words, they are homodynamous
with those of the spinal cord, — and that there are in sharks
fourteen pairs of segments.

Whitman has shown by a masterly analysis of the brain and
nervous system of clepsine that the entire nervous system of
annelids may be regarded as a series of brains, and that, nor-
mally, a pair of these nerve-centers, or brains, belongs to each
segment. This, taken in connection with the facts set forth in
this lecture, enables us to look upon the human brain, not as a
homogeneous mass of tissue, but as a complex^ composed of an
aggregation of about fourteen invertebrate brains, all united
into a working whole. We are to understand that its complex-
ity has been brought about through ages of responses to ex-
ternal and internal influences, and its perfection of physiological
action has been gradually attained. It is the highest product of
evolution, the goal towards which, in the morphological world,
nature has been working for countless aeons of time.

NINTH LECTURE.

THE SEGMENTATION OF THE HEAD.i

PROF. J. S. KINGSLEY.

(Tufts College.)

One of the perennial questions is, " How many segments are
there in the vertebrate head ? " We have long realized that
the body of a vertebrate is made up of segments as clearly
marked as those of a grasshopper or crayfish. Is the head
similarly constituted ?

The first one to suggest such a condition was that mystical
naturalist, Oken. As he tells the story, he was walking in the
Harz Forest in 1806, when he found the blanched skull of a
sheep. His remark upon picking it up was, " It is a vertebral
column." The next year, when appointed professor extraordi-
nary at Jena, he took for his inaugural address the subject,
" The significance of the cranial bones," in which he main-
tained that the skull was composed of three vertebrae, — the
eye, jaw, and ear or tongue vertebrae of his nomenclature.
Human skulls separated into these three vertebrae may be had
in the shops to-day, and looking at one of them we are struck
with the genius of Oken's idea.

Thirteen years later Gothe claimed the discovery as his own,
but time has settled the claim in Oken's favor.

Oken's theory maintained at least a tacit acceptance for
many years, and reached its highest expression in the work of
Owen. Oken's followers tried to carry it further and to
include other structures than the skull. Thus in the trunk-

1 The complete paper, of which this is a short abstract, will be published else-
where at an early date, with full references to the literature, etc.

138 BIOLOGICAL LECTURES.

region the nerves find their exit between the vertebrae, and so
they should do in the cranial region, the number of such seg-
mental nerves being of course one less than the number of
vertebrae recognized in the head. So those who followed Oken
arranged all the cranial nerves in two groups, while those who
thought they saw an additional or nose vertebra, collected the
nerves in three divisions. Here must be enumerated the labors
of Stieda, Johannes Miiller, Stannius, and others.

Stannius, however, took another set of structures, the gill
clefts, into consideration, and although he admitted only three
groups of these nerves (since he recognized four vertebrae) he
still says that "the number of the branches of each cranial
nerve, and the number of spinal-like (segmental) cranial nerves
is determined not so much by the number of cranial nerves as
by that of the visceral arches."

To Gegenbaur is usually given the credit of building upon
this foundation, but we must not forget that in 1869 Huxley
claimed that no part of the skull was vertebral in its nature,
and that not only skeletal, but all structures should be invoked
in settHng the question. It would not do to make the bones
the basis, and work everything else to fit. So, dismissing the
bones, Huxley took cranial nerves and gill clefts as his basis.
Behind the ear, the nerves split above each cleft, and send a
nerve to each of its margins. Here the relationships are clear,
and the segments can readily be distinguished. In front of
the ear, however, there is more difficulty. The facial nerve
splits in the same way, above what is known in sharks as the
spiracle, a cleft which persists in man as the Eustachian tube.
For the next nerve in front, there is at first sight no cleft, but
Huxley advanced the suggestion, often attributed to Dohrn,
that the mouth had been formed by the coalescence of a pair
of gill slits, and upon this supposition, this nerve, the trigemi-
nal, was partly brought into harmony. But not all of it; there
are branches which go farther forward, and for a cleft for these
the orbito-nasal fissure of the embryo was suggested. Still
another cleft still farther in front was advocated, so that Hux-
ley recognized in the head nine segments, — four in front of the
ear, and five behind.

THE SEGMENTATION OF THE HEAD. 139

Two years later (1871) Gegenbaur attacked the same problem,
and between his results and those of Huxley there is much
similarity. With him the cranial nerves are the primary test,
and he tries to bring the gill clefts into accordance with them.

Of the cranial nerves modern human anatomists recognize
twelve pairs, known by name and number as follows: —

I. Olfactory. VII. Facial.

II. Optic. VIII. Auditory.

III. Oculomotor IX. Glossopharyngeal.

IV. Trochlearis. X. Vagus (Pneumogastric).
V. Trigeminal. XI. Spinal Accessory.

VI. Abducens. XII. Hypoglossal.

Like Huxley, Gegenbaur at once threw three of these out of
discussion, for it was thought that the nerves of special sense —
olfactory, optic, auditory — differed from the rest in their mode
of growth, — were, in fact, outgrowths of the brain proper.
Others, from the nature of their functions, were relegated to a
secondary position. As long ago as 1807, Sir Charles Bell had
pointed out that the nerves of the spinal cord had two roots,
the dorsal one with an enlargement, or ganglion, the ventral
non-ganglionated, and that these roots differed entirely in their
function. Through the dorsal root, sensations were brought
from the peripheral parts to the brain, while through the ven-
tral root the actions of the muscles and other structures were
controlled. Hence, since his time, these roots have been called
respectively sensory and motor. In the brain-region, however,
this distinction of roots is not so clearly shown. Some of the
nerves, like the third, fourth, and sixth, have purely motor
functions, and these motor nerves were consequently relegated
to a secondary position ; dorsal or sensory roots were taken as
a test.

Now, applying these ideas, Gegenbaur concluded that since
the vagus nerve was distributed to several gill clefts, it must
be regarded as a composite nerve, while the glossopharyngeal,
supplying a single cleft, was simple, as also was the facial.
The trigeminal, however, had too many branches to supply a
single cleft, and so this was regarded as a double nerve.

140

BIOLOGICAL LECTURES.

Another feature needs mention. The gill clefts are kept from
collapse by the presence of skeletal strengthening bars in the
tissue between them, and these are known as the visceral or
branchial arches. But there were not enough of these to cor-
respond with all the nerves, so Gegenbaur called in small carti-
lages found in the lips of certain sharks, which he regarded as
remnants of such arches. His whole results are summarized
by him in a table : —

Primary
Visceral
Skeleton.

Modified Visceral Skeleton.

Nerve.

1st Arch

1st

upper Labial Cartilage

Ramus, 2

2d Arch

2d upper

and I St lower Labial

Cartilages

Ramus, 3

- J. rigemini

3d Arch

Mandibular Arch

Facial

4th Arch

Hyoid Arch

Glossopharyngeal

Sth Arch

I St Gill Arch

Ramus branch, i ^

6th Arch

2d Gill Arch

Ramus branch, 2

7th Arch

3d Gill Arch

-Vagi

Ramus branch, 3

Sth Arch

4th Gill Arch

Ramus branch, 4 ^

9th Arch

5th Gill Arch

Gegenbaur did something more ; he gave the vertebrate
theory its final quietus, for he pointed out that in the lowest
fishes, where one would naturally expect, were Oken's view
true, that the vertebrae of the skull would be most typical, the
cranium was actually a solid case without the slightest trace
of segmentation. Further, in the higher groups, cranial " ver-
tebrae " can scarcely be spoken of, since the parts of which they
are composed are largely of dermal origin.

Balfour was the next to introduce a new feature into the
discussion. As is well known, the body cavity or coelom.
becomes divided dorsally with a series of paired pouches which
were formerly thought to give rise to the vertebrae, and hence
were called protovertebrae. They are now known to produce

THE SEGMENTATION OF THE HEAD.

141

the muscles of the trunk, and are called myotomes. In the
trunk-region these are the most markedly segmental of any
structures, and appear very early. Balfour pointed out that the
primitive body cavity extended into the head, and that this por-
tion also becomes divided in much the same way as that of the
trunk. So with him " head-cavities " are the test of cephalic
segmentation. As there is much similarity between his results
and those of his pupil Marshall, we may omit a discussion of
Balfour's conclusions and give those of Marshall in more detail,
merely saying that Balfour recognized only eight segments in
the head, with possibly one more.

Marshall uses both head-cavities and nerves in determining
the segments, and he tried to bring gill slits into harmony with
these. He examined those nerves admittedly segmental, and
formulated the characteristics which a segmental nerve must
have. The results to which this brought him may be seen
from the table, but some explanations may be pardoned.

Segment.

Nerve.

Visceral
Cleft.

Visceral
Arch.

I Preoral

I Olfactory

Olfactory

2 Preoral

III Oculomotor

IV Trochlearis

Lachrymal

Maxillary

3 Oral

V Trigeminal

Buccal

4 Postoral

VII Facial
VI Abducens.

Spiracular

Mandibular

Hyoid

5 Postoral

IX Glossopharyngeal

1st Branchial

1st Branrhial

6 Postoral

X Vagus, I St branch

2d Branchial

7 Postoral

X Vagus, 2d branch

3d Branchial

3d Branchial

8 Postoral

X Vagus, 3d branch

4th Branchial

4th Branchial

9 Postoral

X Vagus, 4th branch

5th Branchial

5 th Branchial

10 Postoral

X Vagus, 5th branch

6th Branchial

6th Branchial

II Postoral

X Vagus, 6th branch

7th Branchial

142 BIOLOGICAL LECTURES.

First, the olfactory nerve was brought into the category of
the segmental nerves, for Marshall points out that in its devel-
opment it resembles the other nerves, and is not a prolongation
of the brain substance, that it possesses a ganglion, and finally
it splits distally to embrace the olfactory organ, just as the facial
or glossopharyngeal splits to pass on either side of the corre-
sponding visceral cleft. From this relationship he is led to
regard the olfactory organ as a gill cleft, comparing the folds of
the Schneiderian membrane with the gills themselves, regard-
less of the fact that the one is ectodermal, the other entodermal
in origin. Second, the fact that the trochlearis arises from the
dorsal crest of the brain, and that the oculomotor was thought
to be primarily connected with the ciliary ganglion, leads Mar-
shall to assign these motor nerves segmental value. The
increase in segments behind is due to the fact that Marshall
regarded sharks like Heptanchus, with seven gill slits, as the
more primitive. Regarding the rest of the table nothing need
now be said, but we must point out, thirdly, that the history
of some of the head-cavities was traced. They were found to be
connected at first, and their separation into distinct bodies was
shown to be independent of the formation of gill slits. The
history of two of these cavities was followed, and these two
were found to give rise to some of the muscles which move
the eyeball.

At almost the same time that Marshall published his last
paper. Van Wijhe gave to the world the results of his studies,
and his paper is one of the most frequently quoted in connec-
tion with the subject. Head-cavities form the basis of his
work, and of these he finds nine in the shark. Since his num-
bering of these has been almost universally followed, we
may enumerate them with some detail, giving their fates as
determined by Van Wijhe. The first pair of cavities are pre-
mandibular in position, and in the later development give rise
to the muscles rectus superior, inferior, internus, and inferior
oblique, all of which are controlled by the oculomotor nerve.
The second cavity is above the mandibular arch, and sends a
branch into it. This cavity gives rise to the superior oblique
eye muscle, and is innervated by the trochlearis nerve. The

THE SEGMENTATION OF THE HEAD.

143

third cavity lies above the hyoid arch, and is finally con-
verted into the external rectus muscle, controlled by the abdu-
cens nerve. The fourth cavity, also, lies partly in the hyoid
arch. The rest follow in regular sequence, interrupted only by
the auditory organ. Of these latter the fourth and fifth degen-
erate, the sixth produces a few small muscle fibers, while the
rest unite in forming the ventral prolongation of the sterno-
hyoid muscle. From these facts Van Wijhe concludes that
there are nine segments in the head, and that the hyoid arch
is really double.

The nerves are carefully studied in connection with these
somites. The olfactory and optic nerves are omitted from the
discussion, since, among other points, they are in front of the
segments. It is interesting to note that Van Wijhe shows
that the optic nerve is really the most anterior of all the cranial
nerves. With the remaining nerves the attempt is made to
distinguish dorsal and ventral roots. The results can be seen
in this condensed copy of Van Wijhe's table : —

i

s-.

Muscles from the
Somite.

Ventral Nerve
Root.

Dorsal Nerve
Root.

■

Rect. sup., inf., int.,
and inf. oblique

Oculomotor

Ophthalmicus
profundus

2

Superior oblique

Trochlearis

Trigeminus
less Ophth. prof.

3

Rectus externus

Abducens

> Acusticofacialis

4

none

none

5

none

none

Glossopharyngeal

6

very rudimentary

not recognizable

'

7
8

9

1 Muscles from skull to
I shoulder girdle, with
1 anterior part of sterno-
J hyoid

V Hypoglossus

Vagus

Since Van Wijhe's time numerous attempts have been made
to add to his structure, and in most of these the nerves have
been made especial objects of study, and the results would be

144 BIOLOGICAL LECTURES,

of great interest had we opportunity for their discussion. Most
of these deal with the components of the several nerves, with
the true relationships of the ciliary ganglion, with the position to
be accorded the eleventh nerve, and with the question whether
there be primitively a dorsal root to the hypoglossal. The head-
cavities, too, are discussed. On the one hand, Rabl, in a most
valuable summary of our knowledge of the whole subject, can-
not find all of Van Wijhe's cavities, while Dohrn does not
regard the eye muscles as comparable to the muscles of the
trunk, — a conclusion to which he is led, among other reasons,
by his view that the lens of the eye is a modified branchial
cleft. On the other hand, there are others who find more head-
cavities than Van Wijhe, and among these is to be enumerated
Miss Piatt, who has found one undoubted cavity in front of the
most anterior one of the Dutch anatomist. Dohrn and Killian
go much further, and find eighteen or nineteen of these struc-
tures, but their work can be dismissed with fevC" words. It is, in
fact, difficult to say what Dohrn' s opinions are. He is most
fertile in hypotheses, and he never takes the trouble to bring
his later views into any harmony with the old ones. At one
time every thickening of ectoderm or entoderm is a gill cleft,
again every hole in the mesoderm is a head-cavity, in the third
view the abducens is a complex of at least six nerves. But we
are getting ahead of our story.

To Froriep and Beard we owe the introduction of a new ele-
ment into the discussion, that termed by Beard ** branchial sense-
organs." These authors independently discovered that certain
of the cranial nerves fuse with the ectoderm a short distance
from the brain. From this fusion two structures are developed :
one the ganglion of the nerve, from which the fibers of the
permanent nerve grow back into the brain ; the other, the more
superficial portion, forms the Anlage of a sense-organ situated
in the branchial region just above a gill cleft. These sense-
organs are regarded by Beard as segmental in nature, and
hence, if we count these sense-organs, we at the same time
count the metameres of the head. So, proceeding on this basis.
Beard finds eleven segments in the head, and arranges the
nerves to fit in the way which can readily be seen from the

THE SEGMENTATION OF THE HEAD.

H5

diagram. Among the interesting features is the recognition
of the olfactory as a segmental nerve ; though the nasal
organ is not regarded as a branchial cleft, but as a sense-
organ (cf. Marshall). The facial is also regarded as a compound
nerve, and the auditory nerve is segmental because it supplies
the ear, which, like the nose, is in the same category of seg-
mental sense-organs.

Z

C/3

Dorsal
Nerve
Root.

Branchial
Cleft.

Nature of

Sense-Organ

OF Cleft.

Ganglion.

Head-
Cavity.

Ventral
Nerve
Root.

I

Olfactory

none

Olfactory
Organ

Olfactory

none

none

II

Radix longa
of Ciliary
Ganglion.

none, or
Hypophysis

Branchial

Ciliary

first

Oculo-
motor

III

Trigeminus

Mouth

Branchial

Gasserian

second

Trochlear

IV
V

)■ Facial -

absent
Branchial

Branchial
Branchial

r Facial ■

third

Abducens
none

VI

Auditory

none

Auditory
Organ

Auditory

none

none

VII

Glosso-
pharyngeal

1st Branchial

Branchial

Glosso-
pharyngeal

?

none

VIII

Vagus I

2d Branchial

Branchial

Vagus I

none

none

IX

X

XI

1 Vagus II,
\ III, and
IV

3d, 4th, and J
5th Branchial

Branchial
Branchial
Branchial

1 Vagus II,
\ III, and

none

none

In the year preceding Beard's paper Ahlborn maintained that
there were two distinct kinds of segmentation in the head, — the
one of the mesoderm, mesomery, the other of the alimentary
canal, branchiomery, — and that these two were independent and
not causally related. His views have had not a little influence
on subsequent work, but it must be said that it is not a difficult
matter to answer his arguments, and indeed to show that, so
far as our present knowledge goes, branchiomery and mesomery
are in good accord.

146 BIOLOGICAL LECTURES.

Within the last few years another test of segmentation has
been adduced, that of the segments (neuromeres or encephalo-
meres) of the brain. These structures had been noticed by
several of the older writers upon the development of the ner-
vous system, but little weight was given them until Kupffer
brought them prominently into notice as possibly affording
another clue to the segmentation of the head. The idea was
further carried out by Beranek, Orr, Waters, McClure, Zimmer-
mann, and others, and may be stated in its present form some-
what as follows. Besides the division of the brain into its
several regions, — fore-brain, 'twixt-brain, etc., — this structure
shows in its earlier stages another segmentation, most plainly
seen in its lateral walls. For instance, the medullary region is
seen to consist laterally of a series of paired enlargements, sep-
arated by vertical constrictions, and of these back to the vagus
there are six (Orr) or seven (Hoffmann). These neuromeres
bear a definite relation to the nerves, one pair of these arising
from each neuromere, except that between the acusticofacialis
and glossopharyngeal. 1 In the other brain-regions there are
four more of these enlargements, two in the primitive fore-brain
and two in the mid-brain, — a total of eleven back to and includ-
ing the vagus.

Hoffmann has made a most important discovery in connection
with the development of the cranial nerves. He finds that the
segmental head nerves and the dorsal roots of the spinal nerve
arise not from a solid neural crest, but are paired segmental
out-pocketings {Ausstulpungen) of the dorsal part of the ner-
vous cord itself. For the details of the matter reference must
be made to Hoffmann's paper, but we may point out that a most
important inference is to be drawn from this account. Briefly,
then, the segmental cranial nerves (trigeminal, glossopharyngeal,
etc.) arise as hollow outgrowths from the wall of the cerebral
tube ; these outgrowths reach the skin of the sides of the head,
fuse with it, and from the thickening thus produced the ganglion
of the nerve is formed. From this ganglion the permanent
nerve grows back to the brain, the primary nerve disappearing.

1 Hoffmann finds an Anlage of a nerve here at an early stage. It later aborts,
and cannot be regarded as forming a part of the auditory nerve.

THE SEGMENTATION OF THE HEAD. 147

Exactly the same conditions occur in the formation of the optic
nerve. It arises as a hollow outgrowth from the dorsal ^ part
of the wall of the brain, which reaches the ectoderm, if it does
not actually fuse with it. From the distal portion of this out-
growth is formed the ganglionic layer of the retina, correspond-
ing exactly to the Anlage of the gasserian ganglion, and from
this ganglionic layer the observations of Keibel, Froriep, and
Assheton have shown that the permanent optic nerve grows
back to the brain, the primitive optic stalk becoming aborted.
So that, then, there appears no escape from the view that the
optic nerve, instead of being a structure siii generis, is clearly
homologous with the other admittedly segmental cranial nerves,
— trigeminal, glossopharyngeal, etc. The same discovery also
opens up other possibilities ; besides offering a possible explan-
ation of the mooted question of the origin of the vertebrate eye,
it renders it necessary to take into account in considering the
neural segmentation of the head the little understood pinealis
and the secondary epiphysial structures, for, as Locy has shown,
there are two paired outgrowths from the brain walls behind,
and apparently serially homologous with the optic outgrowths,
and these become developed into what we may collectively
term the epiphysial structures. It is hence possible that we
are to look in this region for some of the long-sought dorsal
roots.

Lastly to be mentioned is the earlier segmentation of the
neural structures discovered by Locy. He points out that in
the very early stages of the embryos of elasmobranchs, batra-
chians, and the chick, before the medullary plate has begun to
close, its margins are ornamented with a series of bead-like
prominences, and that the series of these are continued back
into the trunk-region, and in elasmobranchs they can even be
traced into the embryonic rim (affording some puzzling prob-
lems to those who deny concrescence in the formation of the
vertebrate embryo). In the expanded head-plate of the dog-fish
he finds eleven of these beads on either side, and, following the
history of these through until other landmarks come into view,

1 Morphologically dorsal ; the later hypertrophy of the posterior part of the
dorsal surface forces it to an apparently ventral position.

148 BIOLOGICAL LECTURES.

concludes that the eleventh of these coincides with the position
of the future vagus. The fate of these beads is followed with
some detail, and is regarded as of paramount importance in
settling the vexed question of the metamerism of the head.

It may be that further observations will show that Locy is
right, but more evidence is greatly to be desired. That the
structures in question really exist is beyond doubt ; that they
have the significance which he ascribes to them is far more prob-
lematical. In the opinions of others who have studied them
the structures are less regular and less symmetrical than
described, and their number is not constant. Besides, there
are several discrepancies in Locy's figures, which, without
explanation, seem to invalidate his conclusions. At present it
seems too early to extend the term neuromeres to include these
structures.

It is now nearly ninety years since the question of the
segmentation of the head was first broached. Can we say to-
day how many segments compose this complicated structure }
Several times it has seemed that the answer was close at hand,
but as frequently has the investigation of other features thrown
doubts upon the previous results ; and to-day, while we can say
that there are certainly more than the three or four of Oken
and his followers, we cannot say exactly what the number is.
Before the answer is placed beyond a doubt, a number of other
questions must be solved, not the least of which is the broader
problem of the origin of metamerism and the relation of this
condition in the vertebrates to that in the lower forms.

TENTH LECTURE.

BIBLIOGRAPHY, — A STUDY OF RESOURCES.

CHARLES SEDGWICK MINOT.

The growth of science depends on three things : —

First. The unknown, which is discoverable.

Second. Raw knowledge.

Third. Assimilated knowledge.

Our laboratory has for its special purpose to work in the
first of these fields, and every one of you ought to gain largely
from the discipline and inspiration here placed at your com-
mand. Bibliography inventories the resources of the second
and third field, while text-books are intended to give compre-
hensive surveys of the third. Now text-books are not exces-
sively numerous, and it is not really difficult in this age of
incessant advertisement to keep tally of the best text-books,
their successive editions, and new rivals in one's special field
of biology. Far different is the case when one wishes to
retain command of the literature of original research, where
the gains of raw knowledge, as I have called it above, are
made. It needs but little experience to teach even the begin-
ning student that it is excessively difficult to keep track of the
numerous publications in which the current work, even in a
narrow field of biology, is recorded. With these difficulties
you are all more or less familiar, and know from your own
experience that they are due chiefly to two factors : first, the
very great number of the publications; second, their being
scattered without law or order in many different publications
issued in many different languages. The biological bibliogra-
pher is like an explorer in a forest, — he finds no open way
to travel, but must laboriously hunt for the specimens which

150 BIOLOGICAL LECTURES.

belong in the same class according to our intellectual systems,
and which he must discover as they lie scattered, unclassified,
and, all too often, concealed. In passing, let me add that one
reason for the increase in number of biological articles is the
change in the publication habits of the present as compared
with those of a generation ago. Formerly the preparation of
long and thorough monographs was the goal of ambitious
investigators, but now it is the fashion to publish instead a
succession of short papers. How new this tendency is you
will appreciate easily by remembering that we have now a
goodly number of journals devoted exclusively to very short
papers, such as the Zoologischer AnzeigeVi Bota^iisches Central-
blatt, Bibliographie Anatomique^ and many more, all of which
date back only a very few years. They represent a class of
scientific serials which twenty-five years ago was almost, if
not quite, unknown.

It will be the main purpose of this lecture to point out the
resources we have for finding the literature of a given bio-
logical theme. Before beginning this task let us consider
briefly what a biological author may do to facilitate making a
satisfactory bibliographical record of an article of his own.
We may leave apart the literary and scientific qualities of the
article, not because we fail to assign them their due prime
importance, but only because we are looking at the matter
from the narrower point of view of the bibliographer. Now,
from this standpoint there are five points which seem to me to
deserve special attention.

I. The title, which should be as brief as possible and never-
theless indicate the contents. I recently noted an article
entitled A Reply after Two Years. Under what head will
you enter it } When you read it you will discover that it deals
with the embryology of turtles. Such a title is unpardonable,
for it will cause quite unnecessary trouble to hundreds, per-
haps thousands of people. It is quite as bad as the bugbear
title of the medical bibliographer, A^ Rare Case. There are
thousands of articles on that subject, but what is it } asks the
despairing recorder. For brevity of title it is surely unneces-
sary to plead. Every one who has had to cite authorities

BIBLIOGRAPHY, — A STUDY OF RESOURCES. 151

knows the vexation of having to copy a long-winded title.
What a blessing it would be could we have a Linnaean system
for the nomenclature of biological memoirs as well as of
natural species !

2. The table of contents. The use of tables of contents for
single articles of forty to one hundred or more pages is a
recent and excellent innovation. It gives a detailed summary
of the arrangement of topics, which is often of the greatest
convenience. If you examine the ten volumes of our own
JoiiVfial of Morphology^ you will find many articles with tables
of contents prefixed. Thus, in volume ten there are eleven
articles, five of which — those by Lillie, Strong, Fish, Eycle-
shymer, and Morgan — have tables of contents, and of the
remaining six, only one exceeds thirty pages in length. In
European articles you will find the custom less frequently
followed. I think that you will encounter other indications
that bibliographical usages are more advanced in America than
abroad. May we not attribute this difference in part to the
examples set by our numerous public libraries }

3. Reprints should always preserve the paging of the original
publication, otherwise they cannot be used for consultation or
reference without needless difficulty. Publishers are wofully
behindhand in this matter, and usually change the paging in
reprints, sometimes even in the face of the author's protest, as
I have myself recently experienced. If the paging is changed,
how can we refer to any special page until we have put aside
the reprint and gone to the original publication, the page
number of which alone has the right to be cited }

4. References to other authorities need careful arrangement.
If they are few, it does very well to place them at the bottom
of the page. If they are numerous, the best place for them is
at the end of the article, in alphabetical order by authors.
For reference numbers for the single articles, there are two
chief systems in vogue. One system, the older of the two,
simply numbers the articles consecutively, so that when the
article is completed the manuscript must be revised and the
proper numbers inserted in the text. Theoretically the system
is very simple and convenient, but you will soon learn that in

152 BIOLOGICAL LECTURES.

practice authors are apt to blunder and insert wrong numbers
in the text. One set of references has to be used while
writing, and when all is done another set substituted, and
during the substitution mistakes are not infrequent. The
other system was introduced by Professor E. L. Mark, and has
met with increasing favor. In this system each article is
identified by the name of the author, the date of publication,
and an arbitrary catalogue sign, which last may be a single
letter or digit. For example : —

Mark, E. L. 81.1. Maturation, Fecundation, and Segmentation of
Limax campestris, Binney. Bull. Mus. Comp. Zool., VI, 171-625,
Pis. I-V.

indicates all that is necessary. The figures 8 1 . i stand for the
year 1881, the digits indicating the century being omitted for
all years of the present century ; and the single digit after the
period indicates the arbitrary order of entry, — in this case
that the article in question is the first one to be recorded for
that author and year. Should a second article published by
Professor Mark in 1881 appear in the list, it would be 81.2; but
were it in 1882, it would be 82.1. Professor Mark uses a
slightly different notation, letters serving for entry signs ; thus
the paper just cited would be recorded

Mark, E. L., '8i%

or,

8i^ Mark, E. L.

The apostrophe indicates that the two digits are omitted, but
now that this system has been widely used, the apostrophe may
be safely left off. If one uses Mark's system, the references
may be all put in as the manuscript is written, and the articles
will then group themselves. Every worker should have a card-
catalogue of the publications in his own field, and to such a
catalogue Mark's system is peculiarly adapted; and if it is used,
it is easy to enter all references in one's manuscript, giving
each paper its notation from the catalogue. While preparing
my Human Embryology I utilized this plan for the several
thousand references made in the course of the work, and can

BIBLIOGRAPHY, — A STUDY OF RESOURCES. I 53

assure you that in practice the plan is very convenient and
time-saving. Some of the best investigators prefer other
methods of citing authorities. I can only recommend the two
methods just indicated as best in my own judgment, and add
that it is more important to have a good method than to have
any special method.

5. Spare your readers long abstracts of previous papers.
Omit most of the abstracts you are tempted to insert, and
make those you do give as brief as possible. Abstracts at best
are inadequate repetitions, and save in exceptional instances
should be avoided, especially since there has developed such
an elaborate machinery for the publication of abstracts of all
important and many unimportant papers. Too often an abstract
is tacked on not for any useful purpose, but only to prove that
the author has read the original. On the other hand, a compre-
hensive review of the results collated from a number of publi-
cations may often be valuable, while separate abstracts of the
same papers would be almost valueless.

About the arrangement of one's own library let me inter-
polate a few observations. Of course if a library is small, by
which I mean of less than 500 volumes and pamphlets, no
special arrangement is needed, beyond what may be the out-
come of one's personal convenience. And, on the other hand,
if your library be very large, you must adopt a thorough library
system. Most working naturalists have, however, libraries of
moderate size, the orderly and convenient arrangement of
which is often a perplexing problem. The perplexity arises
chiefly from the accumulation of pamphlets, which are a very
valuable part of a worker's scientific library, being for the most
part reprints of articles in his own special field. Now, there
are three prevalent ways of treating pamphlets.

1. Bind them in volumes by authors.

2. Bind them in volumes by subjects.

3. Arrange them in boxes.

Of these three methods the last is the simplest, most expedi-
tious, and for a library without a catalogue the most convenient.
The boxes readily serve for a classification either by authors or
subjects, as you may prefer. Of boxes for this purpose I

154 BIOLOGICAL LECTURES.

recommend either the cheap pamphlet cases of Manilla paper,
sold by stationers everywhere, or else the more convenient
wooden box devised by Dr. Bowditch, and which has the
advantage that when it is opened the titles of the pamphlets
face you.

[Since this lecture was delivered I have used another form
of pamphlet box, which seems preferable to those mentioned.
It is a box made of whitewood, covered with marbled paper ;
it measures 4x11x7^ inches; it has a common drawer-
handle on the back, and is open at the front, ^ Such boxes are
placed on shelves, like volumes ; they present a neat appearance,
and are easily pulled out or replaced. It would be desirable to
have a card-holder on the back to indicate the contents upon
cards, which can be changed as convenient.]

Every professional biologist ought to have a card-catalogue,
serving the double purpose of a bibliography and a catalogue
of his library. I can probably lay my suggestions before you
most rapidly by describing my own system, which, with your
permission, I will now do. This system has worked satisfac-
torily, but I can by no means claim for it that it is, like
Pangloss' world, the best of all possible systems. The library
is arranged in several groups, and the pamphlets in each group
are arranged alphabetically by authors, and under each author
by Mark's chronological system. First the pamphlets are sep-
arated into two primary divisions, those which are not cata-
logued and those which are catalogued. Those pamphlets
which do not immediately concern my own lines of study are
not catalogued, but are simply classified in Bowditch boxes by
subjects. Thus I have a box for biographical notices, for path-
ology, botany, systematic entomology, microscopical methods,
etc., and hundreds of pamphlets are kept readily accessible.
The remaining pamphlets are all catalogued on cards of the
larger standard library size, made of cardboard, not paper.
Were I to start over again, I should unhesitatingly use the
smaller card, 12.5x5.0 cm. (about 5x2 inches), of stiff paper.

1 Pamphlet boxes as described, but without handles, may be obtained of the
Library Bureau in Boston. In fastening on the handle, fairly large screws should
be used, which may be cut off so as not to project inside and tear the pamphlets.

BIBLIOGRAPHY,— A STUDY OF RESOURCES. 155

The plan on which the cards are written is indicated by
the following form : —

Whitman, Charles O. M. 1893. i

The Inadequacy of the Cell-Theory of Development.
! Journ. Morph., VIII, 639-658.

The upper right-hand corner contains the catalogue number
(Mark's system), the M showing that the pamphlet is in my
collection, and that the card is not merely a bibliographical
one. It is better to have the catalogue number on the left, for
it is then less likely to be covered by the hand in turning over
the cards. The Roman numerals are used to designate the
volume, the Arabic the pages. When there are plates, the
numbers of those are given also. The exclamation point at
the left indicates that the card has been verified by comparison
with the original publication. All my catalogued pamphlets
are divided into three sets: (i) octavo unbound pamphlets;
(2) octavo bound pamphlets ; (3) quarto pamphlets, whether
bound or unbound. When a pamphlet is bound, the card is
marked *' Bd." In each of the three sets the pamphlets are
arranged by authors, and those of each author chronologically.
Thicker pamphlets are bound singly, thinner pamphlets several
together, — but binding many papers in one volume is sys-
tematically avoided. The binding costs from twelve to eigh-
teen cents ; the backs are plain black cloth, with a white paper
label, on which the author's name and the catalogue numbers
of the pamphlets are written by hand ; the sides are covered
with marbled paper. The unbound octavo pamphlets are kept
in Manilla paper pamphlet-boxes. From time to time I look
them through to select those which I wish to have bound.

The system described is simple, and to me it has seemed
convenient and altogether satisfactory, so that I am ready to
recommend it, though of course some other system may be
equally good for private use.

My catalogue serves me also as a bibliography, and I main-
tain a list of titles, which are copied from my cards and
grouped under subjects. In this way I compiled my Bibliog^-

156 BIOLOGICAL LECTURES.

raphy of Vertebrate Embryology^ which was published by the
Boston Society of Natural History in 1893. It contains 3555
titles, and it may interest you to know that I have collected
since its publication upwards of a thousand titles to be added
to it. As this work is intended to result in publication, the
results are written out on sheets of paper, each sheet for one
subject only ; were it not for publication, I should use cards
for the subject catalogue also.

Let us pass to our main topic, a discussion of the means of
looking up the literature of a given subject in the domain of
animal morphology or physiology ; in regard to other divisions
of the wide territory of biology I am not competent to advise
you. We will pass in review : (I) the standard bibliogra-
phies ; (II) incidental bibliographies, given in connection with
special memoirs, etc. ; (III) current bibliographies, which we
can divide into two groups : {A) those appearing annually, and
{B) those appearing periodically at intervals of less than a year.

I. Standard Bibliographies. — The purpose and character
of these is so evident that it is only necessary to enumerate
them. They are : —

1. W. Engelmann. Bibliotheca historico-naturalis . i vol.
8vo. Leipzig, 1846. Covers the literature of 1 700-1 846.

2. Carus und Engelmann. Bibliotheca zoologica. 2 vols.
8vo. 1 86 1. Covers the years of 1 846-1 860.

3. Taschenberg. Bibliotheca zoologica II. Twelve parts,
with pages 1-3888, have been issued, the mammals not being
yet reached. It is the continuation of Carus and Engelmann.

4. Hagen. Bibliotheca ent onto logic a. Die Literatur liber
das ganze Gebiet der Entomologie bis zum Jahre 1862. 2 vols.
8vo. 1862.

5. MiNOT. Bibliography of Vertebrate Embryology. 4to.
Boston Society of Natural History. 1893.

Important help in finding a paper, when the author is known,
is given by the Catalogue of Scientific Papers, issued by the
Royal Society of London, in spite of the enormous number of
its omissions. This catalogue comprises, in all, three series of

BIBLIOGRAPHY, — A STUDY OF RESOURCES. I 57

large quarto volumes. The first series, in six volumes, deals
with the literature of 1 800-1 863; the second series, in two
volumes, with the literature of 1 864-1 873 ; the third, and still
unfinished series, with the literature of 1 874-1 883. It arranges
the papers by authors, numbering those of each author con-
secutively through the three series. There is no classification
by subjects, and no subject index, so that one can obtain a
reference only in case the author is correctly known. On the
score of convenience it is to be regretted that the Royal
Society did not imitate the compact American model of library
catalogue, but on the contrary adopted a type and arrange-
ment which has rendered their volumes needlessly bulky and
inconvenient.

Three other works, though not strictly bibliographical in the
sense of those above mentioned, deserve to be named here.
These are : —

1. Nomenclator zoologicus continens nomina systematica
generum animalium tam viventium quam fossilium, auctore
L. Agassiz. Soloduri, 1 842-1 846. 2d edition, 1848.

2. Nomenclator zoologicus, etc. A comite Augusto de
Marschall.

3. Nomenclator zoologicus, by Samuel H. Scudder.

Agassiz's work contained (2d edition) 32,964 entries, Mar-
schall's 19,966, Scudder's about 80,000. Mr. Scudder's work,
like everything done by the distinguished president of the
Marine Biological Laboratory, is a monument of painstaking
industry and well-directed thoroughness, and it should be at
hand for every zoologist to consult who has a new genus to
name, so that needless duplication may be avoided. Scudder's
Nomenclator was published as Bulletin No. 19 of the United
States National Museum. It was based on Agassiz's Nomen-
clator, together with the manuscript addenda, which Professor
Agassiz had accumulated during a long course of years. It
covers the names introduced down to the close of the year
1879. For later names consult the Zoological Record.

Finally, we are indebted to Mr. Scudder for still another
work, which you will often find invaluable, namely, his Cata-

158 BIOLOGICAL LECTURES.

logue of Scie7itific Serials of all Countries, inchiding the Trans-
actions of Learned Societies iji the Natural, Physical, and
Mathematical Sciences, l6jj-l8y6, published by the Library of
Harvard University in 1879.

II. Incidental Bibliographies, or lists of authorities given in
special works. As you know, every important article gives
more or less extensive references to the previous literature,
and one does not need long experience to appreciate the
immense advantage of this custom. Especially to the great
monographs do we turn for such references, and I may direct
your attention especially to the splendid series known as the
Fauna and Flora of the Gulf of Naples, which is in our library.
The more important text-books usually give carefully selected
lists of the more important papers. You will find such in
McMurrich's Invertebrate Morphology, Wiedersheim's or Gegen-
baur's Comparative Anatomy, Hertwig's Embryology, Korschelt
and Heider's Embryology of Invertebrates, and other similar
hand-books. But among all works of this class there stand
two which are preeminently valuable for their helpfulness in
guiding us to morphological and zoological literature ; one is
Milne-Edwards' Physiologic, in fourteen volumes (G. Masson,
Paris, 1 857-1 881). This great work is a rich treasury of
references, especially to the older literature, which it is some-
what the fashion to overlook, although it often contains things
which have been forgotten, and which you would do well to
make the acquaintance of, if only to learn that the broad
foundations of our science were all laid before any of us were
born. Milne-Edwards was thoroughly versed in the zoological
literature of his time, with, however, a curiously abrupt limit
at about 1858. In fact, though his work contains a very large
number of references to papers later than 1858, the proportion
of omissions is strikingly larger than for papers issued before
that date. You will find the consultation of these early
authorities especially valuable for anatomical information con-
cerning all classes of animals. The present generation is so
devoted to comparative morphology and general principles that
real anatomical knowledge of animals has become almost a
rarity. Thus I find young men who can discuss glibly the

BIBLIOGRAPHY, — A STUDY OF RESOURCES. 159

problem of the morphological (segmental) value of the tri-
geminal nerve, and yet cannot give exact information concerning
it^ anatomical disposition in any animal.

Henri Milne-Edwards was born in 1800, and died in 1885.
He was a typical naturalist, trained under the influence of the
great Cuvier, and as a naturalist looked upon animals very
differently from the modern morphologist, with whose ways he
was as little able to sympathize as with the views of Darwin.
In many respects the naturalist had a broader conception of
zoology than now prevails, for to him the earth was a whole, in
which rocks, animals, and plants all had their parts and mutual
relations, and the comprehension of these relations was the
ideal for the attainment of which he strove. You will find
in Milne-Edwards' writings typical illustrations of the scientific
attitude of zoologists before the Darwinian theory was put
forth, and from these illustrations one preserves an impression
of loss which has befallen us through our surrendering too
fully to the biological tendencies and fashions of our day. It
is therefore doubly profitable to consult Milne-Edwards' Physi-
ologies for it not only collates much information not else-
where well united, but also presents it from a point of view
novel to most of us, although it was the point of view of
those great men who created not only zoology in the nar-
rower sense, but also physiology, comparative anatomy, and
palaeontology.

The other, Bronn's Thierreichy is doubtless well known to
you all. It is a work on a vast plan, aiming, as it does, to
present a comprehensive summary of our knowledge of the
morphology, including also the classification, distribution, and
biology of all classes of the animal kingdom. The volumes are
issued in thin parts, each volume dealing with a single class.
It thus happens that many years have elapsed between the
beginning and the completion of a volume, — the extreme being
the volume on Crustacea, which was begun in 1866 and, al-
though it has acquired great bulk, is still unfinished, though its
author. Professor Gerstaecker, of Greisswald, had at the time
of his death nearly terminated the work. The status of Bronn's
Thierreich at the present time is as follows : —

l6o BIOLOGICAL LECTURES.

Protozoa, first edition, by Bronn, completed 1S59.
Protozoa, second edition, by Biitschli, completed 1889.
Sponges, by Vosmaer, completed 1887.

Actinozoa (coelenterates and echinoderms), by Bronn, completed
i860.

Coelenterates, second edition, by Chun (pts. i-io).
Echinoderms, second edition, by Ludwig (pts. 1-19).
Malacozoa, by Bronn and Keferstein, completed 1866.
Mollusca, second edition, by Simroth (pts. 1-20).
Tunicates, second edition, by Seeliger (pts. 1-3).
Worms, by Pagenstecher and Braun (pts. 1-37).
Crustacea, by Gerstaecker, first half, completed 1879.
Crustacea, by Gerstaecker, second half (pts. 1-46).
Fishes, by Hubrecht (pts. 1-4).
Amphibia, by Hoffmann, completed 1878.
Reptiles, by Hoffmann, completed 1890.
Birds, by Gadow (pts. 1-49).
Mammals, by Giebel and Leche (pts. 1-41).

In all these volumes the literature is abundantly cited, and
they usually include exceedingly valuable bibliographies, in
most cases classified by subjects. When we consider the value
of these lists of authorities, and in our minds add the value of
Bronn' s Thierreich as the fullest existing repository of zoologi-
cal facts, we necessarily rank this invaluable compendium among
the few books indispensable to every zoological laboratory.

III. Current Bibliographies y or periodicals devoted wholly or
in great part to recording the current literature in a given
field. We may consider such bibliographies conveniently
under two heads : firsts annual publications ; second^ periodical,
that is, issued at shorter intervals.

A. Annual Publications. — The succession of these may
be said to have been fathered by Miiller's Archiv fur Anatomie,
Physiologie und wissenschaftliche Medizin. Miiller's Journal
was the continuation of Reil's, Reil and Autenrieth's, and
J. F. Meckel's ArcJiiv. It was begun in 1834, and is continued
to-day, but in 1877 was divided into two Abtheilungen {Anato-
mische and Physiologische), each making an annual volume.
The whole series constitutes the most important morphological
and physiological single publication in the world. Johannes

BIBLIOGRAPHY, — A STUDY OF RESOURCES. l6l

Miiller remained the editor from 1833 to 1858. He was one
of the greatest scientific men Germany has produced, and ranks
as pioneer and founder of three sciences : of comparative anat-
omy and embryology, — or, as we now prefer to say, morphol-
ogy,— of experimental physiology, and of scientific pathology.
He was endowed with that genius for observation and induction
which alone enables a man to become a great leader in natural
science. In the first volume of his Archiv he gives a " Jahres-
bericht ueber die Fortschritte der Anatomischen-physiolo-
gischen Wissenschaften im Jahre 1833." Since that time,
Germany has supplied us our most important annual records
or summaries. The Jahresberichte of Johannes Miiller are
most interesting reading, even to-day ; they are remarkable for
the clearness with which the important points are brought to
notice. In later years he engaged various collaborators in this
work, among whom we find Siebold, Keferstein, Reichert, and
others. With Miiller's death, in 1858, these reports closed.

Their place was taken by two series of Reports, one issued
in connection with the ArcJiiv fur NatiLrgeschichte^ the other in
connection with the Zeitschrift fur Rationelle Medizift. The
former journal was founded in 1835 ^Y Professor Wiegmann,
of Berlin, and originally published with each Heft a report of
progress in some field of zoology or botany ; with its second
year it began the system followed up to the present time, of
issuing two volumes a year, the second made up entirely of
reports for various branches of biology. Of late years the
Archiv fur Naturgeschichte has shown a predominant entomo-
logical tendency, both in its original articles and reports,
although it still continues to cover a wide range, except that
botany has entirely dropped out. Its reports are often very
late in appearing, and are irregularly issued ; thus the part
published in November, 1894, gives the reports on entomology
for 1893, on carcinology for 1891, 1892, and 1893. In spite of
all these peculiarities you will find these Berichte often valuable.

The Zeitschrift fur Rationelle Medizin was a first-class scien-
tific serial. It entered upon its third series in 1857, and then
began issuing, as an annual volume, a ^^ besondere Abtheilung''
the first of which bears this title : ^^ BericJit ilber die Fortschritte

1 62 BIOLOGICAL LECTURES.

der Anatomie und Physiologie im Jahre l8^6. Herausgegeben
von Dr. J. Henle^ Professor in Gottingejt, tmd Dr. G. Meiss?ier,
Professor in Basel!' We have here a consolidation of interests,
for these Berichte, by Henle and Meissner, had already appeared
several years independently. They continued in connection
with the Zeitschrift until 1872 (literature of 187 1). I have
been informed that the cessation of the publication was due
to lack of sufficient financial support. They were, however,
immediately replaced by a new series of Jahresberichte, edited
by Hoffmann and Schwalbe, later by Hermann, of Konigsberg,
and Schwalbe. This new series continued for twenty years,
and it, like its predecessor, ceased, but unfortunately has no
successor, except for the physiological part. But th^sQ Jahres-
berichte are, to a certain extent, replaced on the morphological
side by the Ergebnisse der Anatomie und Entwickelungsge-
schichte, edited^by Fr. Merkel and R. Bonnet, which constitute
the Zweite Abtheilung of the Anatomische Hefte. Of the
^^ Ergebnisse'' three volumes (1891-93) have appeared. These
volumes give comprehensive summaries of groups of articles.
The physiological part of the fahresbefichte has been con-
tinued in a very condensed form by Professor Hermann in his
newly inaugurated series.

With the progress of years the annual reports have gradu-
ally changed in character. The early ones were narrative in
form and critical in character. Thus, in the first report by
Johannes Miiller, he relates the discussions between the sober-
minded, and perhaps dogmatic Cuvier, and the brilliant but
erratic Geoff roy Ste-Hilaire, to whom we habitually refer
erroneously as Ste-Hilaire ; and Miiller indicates his estimate
of both these eminent naturalists, and finds occasion from time to
time to interpolate opinions, and even observations of his own.
But gradually the personality of the reporter is withdrawn,
until it has become the admitted requirement that all analyses
should be impersonal abstracts. In the Jahresberichte of the
present this requirement is entirely fulfilled, with only very
rare exceptions.

There are also two series of ^-^^oSA Jahresberichte^ which the
active worker in biology and zoology will find indispensable in

BIBLIOGRAPHY, — A STUDY OF RESOURCES. 1 63

connection with certain lines of work. The first of these is
edited by Professor Baumgarten, formerly of Konigsberg, at
present of Tubingen. This annual bears the somewhat lengthy
title, Jahresbericht iiber die Fortschritte in der Lehre von den
patJiogenen Miki^oorganismen, timfassend Bacterien^ Pilze tind
Protozoen. The first volume covered the literature for 1885,
and the ninth volume (for 1893) is now in course of publica-
tion. The second of these is the Jahresbericht iiber die Fort-
schritte der Thierchemie, edited by Prof. Richard Maly, of
which the first volume, published in 1873, at Vienna, covers
the literature for 1871. The series is still continued, but the
volumes make their appearance considerably belated.

Finally, I ought to allude — I cannot do more than that —
to the botanical Jahresbericht y the first of whose bulky volumes
was issued in 1873 by Professor Just. In appearance and
arrangement of the contents this series has been closely
imitated by the younger zoological Jahresbericht (begun in
1879).

We now come to the two great zoological records. Those
which have been mentioned above are (with the exception of
the Botanischer Jahresbericht and the reports in the Archiv fur
Naturgeschichte) all prepared in the interest of medical men,
and treat their various subjects mainly, if not exclusively, from
the medical standpoint. The two publications now to be men-
tioned are, on the contrary, adapted primarily to the needs of
zoologists. I refer, of course, to the Zoological Record and to
the Zoologischer Jahresbericht, issued by the Zoological Station
at Naples.

The Zoological Record was founded by Dr. Albert C. L. G.
Giinther, who states in the preface to the first volume, covering
the literature of 1864, that "the object of the Record is to
give in an annual volume reports on, abstracts of, and an index
to the various zoological publications which have appeared in
the preceding year ; to acquaint zoologists with the progress of
every branch of their science in all parts of the globe ; and to
form a repertory which will retain its value for the student of
future years." The Zoological Record has to a certain extent
attained its objects, and is, indeed, an invaluable aid in finding

1 64 • BIOLOGICAL LECTURES.

the literature of any subject. It has suffered in reputation
very much, owing to its incompleteness, its omissions being
very numerous, and too often both surprising and inexcusable.
You have only to compare the volumes from Naples with those
of the Record for the corresponding years to satisfy your-
selves that the criticism made is perfectly just. When, there-
fore, you consult the Record, you will usually find that there
are other perhaps important articles on your subject besides
those cited in the Record. The English standard of bibliog-
raphy appears to me not to be very high either in regard to
practical details of arrangement, or in regard to thoroughness.
I remember that when Mr. Scudder prepared his list of sci-
entific serials he found a large number which were entirely
overlooked by the Royal Society in their great catalogue. In
1870 a special association was formed, which many naturalists
joined, for the object of continuing the Record. In 1887 the
publication was assumed by the Zoological Society. The
yearly Record is sometimes more or less incomplete ; thus in
the volume for 1894 the reports on Crustacea, Arachnida,
Myriapods, and Vermes are lacking. Incredible as it seems in
such a work, there is no index of authors, but only an index of
new genera ! In fact, the Record has its chief value as an
assistance to the systematic zoologist.

The Zoologischer Jahresbericht, published by the Zoological
Station at Naples, is a very thorough and admirable work. Its
first seven volumes (i 879-1 885) covered the whole field of
zoology, but since then it has omitted all systematic work,
leaving that for the Record. Its matter is well arranged,
and so indexed and printed that it is easy to find what
one seeks. In brief, it is indispensable for every zoological
laboratory in which anything higher than elementary work
is attempted.

B. Periodical Bibliographies. — Under this head we have
to pass in review a series of journals appearing at short inter-
vals. These journals form two natural classes : first, those
specially devoted to bibliography, all of which publish short
original articles ; second, those which are chiefly devoted to
short abstracts of articles published elsewhere.

BIBLIOGRAPHY, — A STUDY OF RESOURCES. 165

First Class (mainly bibliographical). — i. Zoologischer
Anzeiger. This valuable publication is probably well known
to you all. It was founded in 1878 by the veteran zoolo-
gist, Victor Carus, and publishes at frequent intervals lists
of articles grouped according to the class to which they
refer. This plan secures relatively prompt publication of
the titles, but has the disadvantage that consultation of
the completed volumes is exceedingly laborious, for one has
to look through lists scattered irregularly through the pages.
Owing to the enormous growth of zoological literature it was
found necessary to divide the Anzeiger into a volume for
original articles and another exclusively for bibliography.

2. Anatomise her Anzeiger. This journal resembles the
Zoologischer Anzeiger very closely in plan and appearance, but
differs somewhat in its scope, for it confines itself to the litera-
ture which interests the student of vertebrate morphology, and
classifies the titles according to the organs to which the papers
refer. This magazine was founded in 1886 by Karl Bardeleben,
of Jena, and is now the ofificial organ of the German Anatom-
ical Society, whose proceedings are issued as an Ergdnzungsheft
of the Anzeiger.

3. Bibliographie anatomiqiie. A journal of the same general
character as the last, but its bibliographical lists are confined
exclusively to articles published not in France but in French,
— a restriction which necessarily appears somewhat absurd
as well as characteristically provincial to us. The journal,
nevertheless, is an excellent one, and contains valuable original
articles, and a certain number of abstracts, which are usually
good. It is edited by Professor Nicolas, of Nancy, and was
started in 1893.

4. Monitore zoologico. This little magazine is one which
ought to be more widely known in America, and deserves
general support. It set the model for the French publication
last mentioned, for it was started several years earlier, having
begun in 1890. It gives original articles, abstracts, and lists
of papers on zoological and morphological subjects, published
by Italians, whether in the Italian language or not. Now
there is a great deal of important investigation accomplished

1 66 BIOLOGICAL LECTURES.

in Italy, but owing to entire lack of first-class scientific jour-
nals in Italian, the results of these investigations are issued in
all sorts of ways, — oiten in little-known medical journals or
in the transactions of obscure scientific societies, with which
Italy swarms, — and they would remain permanently unknown
were it not for the painstaking records of Professor Chiarugi
in his Monitore.

The four serials just mentioned ought to be accessible to
every student and to form part of the library of every zoolog-
ical or morphological laboratory. The remaining serials to be
enumerated are certainly less essential, but for certain special
purposes are almost indispensably consulted. They form my

Second Class (journals primarily devoted to publishing
abstracts of papers). — I have noted the following : —

1 . Medizmisckes Centralblatt, founded in i863,by L. Hermann.

2. Biologisches Centralblatt, founded in 1 88 1, by J. Rosenthal.

3. Gynaekologisches Centralblatt, founded in 1877, by Dr. H.
Fehling, of Stuttgart, and Dr. H. Fritsch, of Halle.

4. Neurologisches Centralblatt, founded in 1 882, by E. Mendell.

5. Physiologisches Centralblatt^ founded in 1887, by S. Exner
and J. Gad.

6. Zoologisches Centralblatt, founded in 1 894, by A. Schuberg.

7. Fortschritte der Medizin, founded in 1883, by C. Fried-
lander.

8. Journal of the Royal Microscopical Society of London gives
numerous good abstracts of articles interesting to microscopists,
was begun in 1878, is now issued in bi-monthly parts, forming
a bulky annual volume.

9. Virchow-Hirsch Jahresberichte, founded in 1866 as the
continuation of an earlier medical Jahresbericht published at
Erlangen.

10. Schmidt's JahrbUchery which was founded in 1834 and
has grown into a series of nearly two hundred and fifty vol-
umes. These Jahrbilcher are literally indispensable for look-
ing up certain lines of research through the past, as, for
example, the determination of sex, the phenomena of puberty,
menstruation, growth, anatomy, and physiology of infancy,
senile metamorphoses, heredity, etc. On all these subjects

BIBLIOGRAPHY, — A STUDY OF RESOURCES. 1 67

Schmidt' s Jahrbucher will guide you to many articles of bio-
logical interest, which you are little likely to discover otherwise.

It often happens that one cannot obtain a certain original
paper when needed, and in such cases an abstract of the paper
wanted may be found in one or several of the ten serials just
enumerated. You will notice that many of them are medical
journals, and yet they are sometimes indispensable to the
zoologists and morphologists. For example, articles on the
uterus and placenta, on growth, heredity, origin of sex, and
many other subjects are often to be discovered through medi-
cal publications, and through medical publications only.

You have doubtless all been struck with the fact that nearly
all the titles I have quoted are in German or in Latin by Ger-
man authors, and have already reached the conclusion that the
work of the world in recording biological literature is mainly
the work of Germans. This conclusion is correct, and it is a
pleasure to make a public acknowledgement of our indebted-
ness. Hereafter, we hope that a systematic and thorough
record of zoological and anatomical literature will be kept by
the International Bureau organized at Zurich through the
efficient energy of our countryman Mr. H. H. Field. We
should each look upon it as a personal obligation to support
the work of this Bureau, both by cooperating with it and by
subscribing to its publications.

To conclude : how is one to proceed if one wishes to find
the literature of a given zoological or morphological subject.''
I should answer : consult first the principal text-books at your
command, which will give you probably some of the chief
authorities, by turning to which you will obtain other refer-
ences; and from the papers thus traced yet other references
will be secured. Unless one is dealing with some minor or
detailed question, or some novel or unusual topic, one can
usually obtain acquaintance with a considerable body of inves-
tigations with comparative rapidity. Next, one must consult
the standard bibliographies (p. 1 56), and also both the various
Jahi'esberichte and the current bibliographies (especially of the
Zoologischer and of the Anatomischer Anzeiger). Third, con-
sult Milne-Edwards' Physiologie and Bronn's Thierreich ; or, if

1 68 BIOLOGICAL LECTURES.

you can find any important monograph which certainly or
probably deals with your subject, consult that, of course.
Finally, if your question is one medical men are likely to have
discussed, look through the Reports of Virchow-Hirsch and
Schmidt's Jahrbilchery and also through the various medical
journals of the Centralblatt type (see p. i66, above).

I have dealt with a difficult and, I fear, very dry subject,
and can only hope that some of my suggestions will prove
helpful. It is profitable to consider sometimes the ways and
means of science as well as her results, for the investigator's
success depends upon his mastery over both means and results,
and this double mastery can be had only by those who also
command the complex bibliographical resources of biology. I
hope that our review of these resources will encourage some of
you to enter, others to advance along the paths of research ;
and I trust that you all, when you leave the laboratory, will
carry with you a deeper and loftier enthusiasm for original
research, which is at once the chief duty and the chief privi-
lege of the biologist.

Revised at Boston, Dece?nber, 1895.

ELEVENTH LECTURE.

THE TRANSFORMATION OF SPOROPHYLLARY
TO VEGETATIVE ORGANS.^

PROF. GEORGE F. ATKINSON.

(Cornell University, Ithaca, N.Y.)

The general effect of nutrition in plants is evident in their
growth and fruiting ; but the more subtle influences, under a
great variety of changing or special conditions, are but imper-
fectly understood. In general, an increase in food supply
within the plant, external conditions being favorable, increases
the entire plant product. In poor soil plants may be fed with
profit, the product increasing, though not in the same ratio,
with the increased supply of food. Not only is the vegetative
part of the plant increased, but the fruit also, within certain
limits. The ratio of increase, however, between the vegetative
portion of the plant and its fruit is not constant, but changes
with the varying food supply. After a given point the vegeta-
tive portion increases more rapidly than the fruit. Another
striking influence of increased food supply is that a point is
reached soon where the fruit portion decreases, or is even com-
pletely suppressed, while the vegetative portion still increases.
Our knowledge of these disproportionate and antagonistic
relationships between the vegetative and reproductive portions
of the plant is largely empirical, though some of it is based on
direct experimentation. It is not surprising, therefore, that
even among botanists there should be differences of opinion
concerning the fundamental laws governing these relationships.

The genus Onoclea, as well as some others, presents an
interesting dimorphism of the leaves, some of the leaves being

1 See Plates I-VIII at close of volume.

lyo BIOLOGICAL LECTURES.

devoted exclusively to the vegetative function, while others are
devoted exclusively to the reproductive function. In Onoclea
the vegetative leaf forms a large expanded triangular lamina,
which is divided into several large pinnae with rudimentary
lobes or pinnules. The reproductive leaves, or sporophylls,
are built on much the same general plan, but are much shorter,
with the pinnae and pinnules also much shorter and narrower,
and the edges inrolled, entirely concealing the sporangia, as if
they were enclosed in carpellary structures, though the sporo-
phyll has not become a closed structure, such as is found in
the ovary of higher plants. The inrolled pinnae are closely
appressed against the rachis of the sporophyll.

Besides this structural dimorphism of the leaves they present
what is sometimes termed a seasonal dimorphism, — i.e. the
vegetative leaves are the first to appear in the season, from
April and May until July, while the sporophylls appear in July,
or the latter part of June. During the first part of the season
the vegetative or nutritive system of the plant is built up,
while during the latter part of the season the reproductive
function is in the ascendant. Occasionally an abnormal state
of the leaf in Onoclea sensibilis is found, in which both func-
tions are united in a single leaf, a portion of the leaf being
expanded and resembling the vegetative leaf, while some of
the pinnae are* more or less rudimentary, revolute, and sporif-
erous, representing an intermediate stage between the truly
vegetative leaf and the typical sporophyll. This form of the
leaf was once described as a variety — obttisilobata Torrey —
of this species of Onoclea, though later it was regarded as "■ a
rare abnormal state in which the pinnae of some of the sterile
fronds, becoming again pinnatifid, and more or less contracted,
bear some fruit dots without being much revolute or losing
their foliaceous character." ^ The language here suggests that
the sterile leaf becomes partly transformed into a fertile leaf,
in accordance with the old ideas of metamorphosis. More
recently,^ from the discovery of a number of the forms of this

1 Gray's Manual, 5th ed., p. 668. The same form of the plant was known as
the species O. obtusilobata Schkuhr, idem.

^ Underwood : Bull. Torr. Bot. Club, Vol. VIII ; Bot. Gaz., 1881, p. loi.

TRANSFORMATION OF SPOROFHVLLARV. 171

species in a meadow, it was suggested that this state resulted
from some injury to the sterile leaf, so that the vegetative
function was forced upon the very young sporophylls, causing
them to expand more or less, while the sporangia and sori were
correspondingly decreased. This suggestion met with consid-
erable opposition. Later the suggestion was adopted and pub-
lished by another, and upon this the following criticism appeared
in Nature, April 15, 1894 : **The remark quoted . . . about the
probable cause of the cases where the fronds of Onoclea have
an intermediate character between the usual sterile and fertile
conditions, is one of those sage observations which it is easy to
make, but which observed facts hardly or not at all sustain."

Although an experiment had been planned for the purpose
of attempting to induce this form artificially by cutting off the
early vegetative leaves, this criticism really *' set the machinery
in motion," for without experimental proof such an empirical
proposition lacked an essential foundation for argument. The
locality selected for carrying on the experiment was in the
vicinity of Ithaca, N.Y., on the flats not far from the head of
Cayuga Lake. The first cutting of the leaves was made May 1 1,
when they were twelve to eighteen inches high. It was feared
at the time that the experiment had been postponed too long
to obtain the desired results, as it seemed within the bounds
of possibility that already the vegetative function might have
been carried on for a sufficient time for the manufacture of
what carbohydrates the plant would need for the perfect
development of the reproductive portion. The intention was
then to cut the leaves about once each week, in order that the
plants could derive very little benefit from the later developed
sterile leaves. Heavy rains, however, prevented access to the
localities until June 9, when the leaves were cut a second time.
The second leaves had reached approximately the same size as
the first crop, and still by this time there was no sign of the
development of the fertile leaves, either in the experiment plat
or in adjacent plants which had been left as checks.

July 12 a third visit was made to the locality on the Ithaca
flats, where the larger number of ferns were. Diligent search
at this time revealed nothing which at first could be under-

172

BIOLOGICAL LECTURES.

stood to be the fertile leaf in the experiment plat, and the
knife was used for the third time. While cutting the third
crop of leaves occasionally one was seen which appeared quite
different from the ordinary sterile leaves. The pinnules were
fully expanded, and the lobes appeared nearly normal in form,
but the venation was somewhat more prominent, and this gave
the appearance which first attracted attention. After critical
examination there were seen peculiar and very small whitish
flakes or scales on the under surface of the pinnules. These,
with the aid of a pocket lens, were readily seen to be partially
aborted indusia, located either directly across or at the side of
the veinlets. The pleasure at the discovery of this result was
considerably dampened by the thought that the experiment
might prove to have been too radical by cutting the leaves
more than once. Further examination revealed what appeared
to be still younger fertile leaves which would not be so fully
expanded when grown. At this date there were observed in
the adjacent undisturbed plants several normal sporophylls
partially developed. July 29 another examination was made,
and quite a number of leaves were found which would be taken
for quite typical cases of the form of the species.

August 8 and 9, all the plants showing these results were
gathered and photographed, a portion of the stem, or rhizome,
was taken with each plant in order to show some, at least, of
the bases of the leaves which had been amputated, as well as
the recently developed sterile leaves for comparison. Nearly
thirty such plants were gathered, and more than twenty of these
were photographed, in order to preserve an accurate record of
the many variations which presented themselves.

In the normal sporophyll, the pinnae are quite closely
approximated on one side of the rachis. The fertile pinnules
are closely revolute, and the margins very much shortened, so
that each pinnule forms a small, oval, pocket-shaped or slipper-
shaped sack, open only at a point near the attachment with
the mid-vein of the pinna. These pinnules possess two to four
pairs of lateral veinlets. Upon these lateral veinlets are the
placentae, seated rather near the base, and the true indusium
is situated across the base of the veinlet, near, or a little dis-

TRANSFORMATION OF SPOROPHYLLARY. 173

tant from, the mid-vein, and arches slightly outward, or away
from the mid-vein, partially covering the group of sporangia.

The first step in the transformation of the sporophyll is the
lateral spreading of the pinnae, so that they stand out more or
less strongly in a plane corresponding to that of the vegetative
leaf. At the same time there occurs a partial unfolding of the
revolute pinnule. This occurs by an increase in the number
of cells of the lamina, and a corresponding decrease in the
growth of the cells which go to form the sori. The marginal
cells of the lamina increase more rapidly than those toward
the mid-vein and the base. A few of the terminal pinnae in the
normal sporophyll bear no pinnules, but are very much like
the pinnules of the lower pinnae. The simplest condition of the
unfolding of the revolute pinnae or pinnules is the partial
expansion of these terminal ones, more advanced stages pro-
ceeding along down from the terminal portions of the pinnules.

The grades of transition are correlated with the circinate
development of the leaf, the later developed portions showing
a more highly developed vegetative expansion and function
than the early developed portions of the same leaf. The pinnae
then, in the simplest and intermediate stages, have a more
or less clavate or spathulate outline. The pinnules in an indi-
vidual pinna may vary from quite strongly revolute ones to
those which are fully expanded and nearly plane.

Occasionally transformed fertile leaves are found which show
a tendency to an abortive development, i.e. they remain quite
small, the stipe rather short, the pinnae and pinnules very
short, though they may be quite fully expanded.

Comparing individual sporophylls, all grades of transition are
present from the completely differentiated fertile leaf to the
sterile one. In several cases it was impossible to determine
with certainty to which phase of the dimorphism the leaf pri-
marily belonged, or for which it was originally intended. Some
of these leaves which were at first doubtful were finally found
to possess rudimentary indusia on a few of the lower pinnae,
these occurring on the basal pinnules.

The fully or partially expanded pinnules, when the transfor-
mation has not been carried too far, are more or less obtuse.

174 BIOLOGICAL LECTURES.

The venation also is very prominent, and strong in contrast
with that of the sterile leaf, especially the lateral veinlets of
the pinnules. This character is quite persistent, and enables
one to differentiate the leaves frequently when no indusia are
present, and the pinnules are not obtuse, or no more so than
those of the normal sterile leaves.

One transformed sporophyll had a length of twenty-five cm.,
and a spread of pinnae twenty-two cm. in extent. A very few
of the basal pinnules had their margins slightly revolute, and
quite a number of indusia were present, while very few of the
pinnules were obtuse. The venation of the entire leaf was
quite coarse and very prominent.

During the expansion of the pinnules, the position of the
indusia changes somewhat, and its form, to a very great extent.
It becomes located at a greater distance from the base of the
lateral veinlets, the distance depending to some extent upon
the extent of the transformation of the pinnule. In broadly
expanded pinnules at the termination of the pinnae, the indusia
are frequently moved on to veinlets of the second and third
order, instead of those of the first order.

While indusia are present on partially or nearly expanded
pinnules, or frequently on fully expanded ones, sporangia
appear to occur only on those which are entirely normal, or
only partially expanded. Passing through the various transi-
tions of the pinnules, from the normal fertile ones to those
which are little more than half expanded, the sporangia vary,
gradually decreasing in number and perfection of development,
as the pinnules partake more and more of the vegetative char-
acter. In the partially expanded pinnules, the indusium is fre-
quently so small that it affords very little protection to the
sporangia, and the location of rudimentary sporangia is often
at a considerable distance from the indusium.

When the leaf has lost so much of its reproductive function
that the sporangia are becoming rare or rudimentary in the
sorus, apospory frequently occurs, and the placenta develops
among the rudimentary sporangia prothalloid growths. These
are filamentous, lanceolate, or spathulate in form, the two latter
forms being two or more cells wide. The cells are richly pro-

TRANSFORMATION OF SPOROPHYLLARY. 175

vided with chlorophyll, but thus far no antheridia or arche-
gonia have been found. These prothalloid growths resemble
very much some of those which are developed from the placen-
tal region of Pteris aqiiilina L., and first described by Doctor
Farlow in the Annals of Botany, II, 1888, p. 383. The same
condition of Pteris aquilina was noted by myself in the autumn
of 1893, at Ithaca, N. Y.

When the experiment with Onoclea sensibilis was undertaken,
no serious thought was given to an attempt to produce like
conditions by artificial treatment with the other species of this
genus, namely, Onoclea struthiopteris. However, on July 14,
after observing the result which was attending the experiment
with Onoclea sensibilis, I determined to try the Onoclea struthi-
opteris even at this late date. The fern is very abundant on
an island in Fall Creek, where vegetation is very rank and the
leaves of the ostrich fern attain a height of 150 cm. or more.
The leaves from fifty or sixty stools of this fern were cut
away, the leaves then having attained their maximum height
for this locality. In this number of stools there were half a
dozen in which there were fertile leaves already 15-25 cm. in
height.

The experiment was inspected on August 10. The fertile
leaves which were up on the 14th of July had matured their
sporangia and were, to all appearance, normal. There were
many rudimentary fertile leaves only partly unrolled, three to
six inches in height. These were also found among the stools
of the fern which had not been disturbed. For a long time
during the spring, the ground here was under water, and this
may have had some influence in aborting many of these leaves.
That many of them were of the fertile kind was manifest by the
peculiar revolute character of the rudimentary pinnules.

Very few of the stools from which the leaves had been cut
on the 14th of July had put forth new leaves. Ten or twelve
had produced one to four leaves, ranging from one to two feet
high. Very careful search was made to discover some sign of
a sporophyll partially transformed, and I was about to conclude
that the experiment was a failure for that year because entered
upon at so late a date. At last a single leaf was found in a

176 BIOLOGICAL LECTURES.

stool where were three freshly developed sterile leaves. The
sterile leaves were 60-75 cm. in height, and the transformed
sporophyll about 30 cm. The leaf was somewhat injured by
accident, perhaps by the knife when cutting the sterile leaves
on the 14th. The pinnae were fully expanded, yet markedly
different from those of the sterile leaves, being only toothed,
while the pinnae of the sterile leaves are deeply cut and possess
quite acute pinnules. The teeth, or pinnules, of the trans-
formed fertile leaf were obtuse or rounded. This was the only
marked difference at first observed, and I did not feel warranted
in concluding that it was a fertile leaf until examination with a
pocket lens revealed plainly a number of rudimentary indusia.
There were no sporangia, however, not even rudimentary ones,
and none of the pinnules were at all revolute.

The experiment with Onoclea striithiopte}is being somewhat
unsatisfactory, because undertaken so late in the season, was
renewed this year (1895). The first vegetative leaves were cut
early in May, when they were about 40 or 50 cm. long. This
species differs markedly from Onoclea sensibilis in the vernation
of the leaves. Those of Onoclea sensibilis are developed suc-
cessively one by one on a prostrate rhizome, or stem, which
advances so rapidly that the leaves of one season stand in a
row. In Onoclea struthiopteris the stem is perpendicular and
increases in length very slowly, the leaves being developed in
rosettes, a half dozen, more or less, at one time.

The experiment plat was visited a second time early in June,
and a second rosette of leaves had developed from the stools
which had been cut in May. This time the leaves were about
30 cm. high. None of the sporophylls had appeared, and the
leaves were cut again. Leaves from undisturbed plants were
also cut at this date. Late in June a few of the sporophylls
were appearing from a very few of the untreated plants, but
none as yet showed from the amputated plants, though another
large rosette of vegetative leaves had developed. The season
was a very dry one, and very few sporophylls had developed,
and for this reason the experiment was considered a failure.
However, July 29th a sudden impulse seized me to visit the ex-
periment plat again, and this time not in vain, for eight to ten

TRANSFORMATION OF SPOROPHYLLARY. I 77

plants had each from one to four partially transformed sporo-
phylls. These presented a great variety of stages in the transi-
tion, though in no case had the transformed sporophylls reached
the size and expansion of the vegetative leaves as in the case
of Oiioclea scnsibilis. They were quite young, however, and
probably later in the season would have been larger and more
expanded.

These plants were nearly all removed to the laboratory at
the time in order to photograph and study them. In general
the transformation of the sporophylls of Onoclea striithiop-
teris agrees with that of Onoclea sensibilis in that the distal
portion of the leaf and of the pinnae expand more than the
proximal portion, these latter parts bearing either normal sporan-
gia and sori, or showing them in various stages of degradation
and suppression. At that time no prothalloid growths could be
discerned with the eye, or with the aid of a pocket lens. Per-
haps they might appear later in the season, since the sporophylls
were much younger than those on Onoclea sensibilis on which
they occurred.

The results of these experiments are entirely in harmony
with a law which many recognize to exist between the vegetative
and reproductive functions of plants, and indeed animals as
well. They serve, however, to demonstrate clearly this relation
which in many cases has been observed empirically rather than
demonstrated by definite tests. In these ferns, the fact that
there is a complete differentiation between the sterile and fertile
leaves, and that the sterile leaves develop quite far in advance
of the fertile ones, makes the case peculiarly adapted to present
a beautiful demonstration of the law. A certain development
of the vegetative phase is necessary in order to provide for the
necessary nutriment which the reproductive phase requires. If
the vegetative leaves are destroyed or removed before this func-
tion is so far completed as to enable the complete development
of the reproductive phase, the latter will necessarily decrease,
and there will be an effort on the part of the plant to provide
as quickly as possible for the furtherance of the vegetative
functions. This can most quickly be attained by the partial or
complete expansion of leaves which had begun to be differen-

IjS BIOLOGICAL LECTURES.

tiated as fertile ones, for the general plan of structure of the
sterile and fertile leaves is very much the same, especially in a
very early stage of their development. The different degrees
of fixation of the reproductive characters on these very young
fertile leaves, at the time when the plant is suddenly deprived
of the fully developed vegetative leaves, determines to a great
extent the individual character of the transformed structure
which assumes the responsibility for the entire labor of the leaf
system heretofore definitely divided between different individual
leaves or structures. This individual character is also influ-
enced to a certain extent by the readiness with which the indi-
vidual plant puts forth new vegetative leaves. So with the
various combinations of these two conditions there results the
very wide variation which is here presented in the forms of
the transformed fertile leaves, showing almost every conceivable
gradation which we could naturally expect when we take into
consideration the course of development of the ordinary leaves.
The extremes of these variations present very doubtful cases.
On the one hand, there are fertile leaves which have felt the
slightest touch of this influence controlling the transformation,
and it is extremely difficult to say whether it is entirely normal
or not. On the other hand, there are cases where the greatest
demand has been made upon a leaf of the fertile kind at so
early a period in its development that it becomes to all intents
and purposes a vegetative leaf, and possesses so little of the
individuality of the fertile leaf that we cannot, in our ignorance,
discriminate it from a leaf of the vegetative kind.

The plan this season, though not carefully originated, was to
extend the experiments to phanerogamous plants in order to see,
especially, if the pistils, which are supposed to be homologous
sporophyllary organs, could be forced to take on the form and
function of the vegetative leaves by cutting off the latter. This
part of the experiment, I say, was not well originated, since,
on account of numerous other duties, no selection of plants
was made until operations were begun in the spring. For this
reason some of the plants operated on were too far advanced,
while others were ill chosen, because the sporophylls appeared
at the same time as the vegetative leaves. This latter difficulty

TRANSFORMATION OF SPOROPHYLLARY. 179

presented itself especially in the case of Podophyllum peltatum,
Ariscema tripJiylltirn, and Aralia midicaulis. In Geranium
macuiatumy Smilacina racetnosa^ Angelica atropiirpiirea^ and
Veratrum viride the sporophyllary organs were too far advanced.

While direct experimental evidence seems to be lacking,
there is enough of empirical evidence to show that the trans-
formation of the sporophyllary organs to vegetative ones takes
place quite frequently in certain species of the phanerogams.

Transformations of the andraecium, or stamens (microsporo-
phylls), is not a very common occurrence, though it is recorded
in the case of several species. Petunia^ Jatropha pohliana Miill.
(Muller, Mem. Soc. Phys. et Hist. Nat., Geneva, Tome XVII),
Trifolium repens, cultivated species of Rosa, etc. Transforma-
tions of the pistils, or gynaecium (macrosporophylls), are much
more common and remarkable. In the double-flowering cherry
the ovary is changed often to a small foliar organ, frequently
the margins separated thus exposing the ovules, while the tip
has a slender style and imperfect stigma. Moquin relates a
case in a tulip where the ovary was represented by true leaves
with ovules on their margins. This frequently happens in the
columbine and in members of the Cruciferae and Umbelliferse.
In Vitis sometimes the pistil is foliaceous, with the ovules on
their inner surface (Planchon et Mares, An7t. Sci. Nat,, Ser. 5,
Tome VI, p. 228, 1866). If the ovary is the homologue of the
macrosporophyll in the strobilus of the Archegoniatae, as Bower
suggests, then the opening of the ovary and the exposure of
the ovules, or macrosporangia, under the influence of changed
or disturbed conditions of nutrition, must be looked upon as a
partial reversion inform only, not a reversion in function. This
is accompanied by a more or less complete sterilization of the
sporogenous tissue, the expansion of the blade into a well-
developed foliar organ, and the assumption of the vegetative
function in place of the reproductive one.

The philosophy of these changes, viewed not only in the light
of immediate causes, but also from the standpoint of phylogeny
of the foliar organs of the sporophyte, teaches that they proceed
from the sporophyllary to the vegetative organs. This study
has led rather unexpectedly to questions of deeper import than

l8o BIOLOGICAL LECTURES.

were in mind at the start. It suggests more than the mere
adaptation of the sporophyll to the form and function of the
vegetative leaf, directed by some influence which tends at the
time to force that function on it. It suggests that in general
vegetative leaves may have been derived from sporophylls.

In other words, these results lend force to the proposition
offered by Bower {Ann. Bot.y VIII, pp. 343-365, 1894) that the
sporophylls are primary organs, the vegetative leaves secondary
ones, and that sporophylls never have been derived from foliage
shoots, but that the converse is true.

Aside from the questions of homology and phylogeny of foli-
age shoots and sporophylls, another one presents itself, which
suggests that one of the potent influences in the evolution of
vegetative organs on the sporophyte was a disturbance of the
carbon assimilatory function of the gametophyte in the gradual
passage of plants from an aquatic to a terrestrial life. This is
a purely theoretical consideration, and probably must always
reniain so, though it is quite probable that artificial injury to the
gametophyte could be made to result in the sterilization of
sporogenous tissue, which was the first step toward the evolu-
tion of sporophytic vegetative organs. However, considering
the sporophyte alone, we have seen how artificial injury can be
made to influence the advance of a sporophyll to a foliage shoot
within a single life cycle, — a demonstration of phylogeny in
ontogeny.

rRANSFORXfATlOX OF UPOROI'H VIJ.AKY. iSl

Y

Pi.ATK T. — Onoclea Sensibilis, normal form.

l82

BIOLOGICAL LECTURES.

Plate II. — Oiioclea Sensibilis, with partially transformed sporophylls

TRANSFORMATION OF SPOROPH YLLA RY. 183

Plate III. — Onoclea Sensibilis, with partially transformed sporophyll.

1 84

BIOL OGICA L A EC TURKS.

PLATii IV. — Onoclea Sensibilis, with two completely transformed sporophylls.

TRANSFORMATION OF STOROTH VLI.ARV. I 85

Plate V. — Onoclea Sensibilis. a normal form of sporophyll. b partially transformed
sporophyll, showing " fruit dots."

1 86

BrOT. OGICA L LECTURES.

Plate VI. — Ouoclea Sensibilis, lower portion of partially transformed sporophyll magnified.

TRANSFORMATION OF SPOROPHVLLA RV. 187

Plate VII. — Onoclea Struthiopteris. The four small leaves are sporophylls : one is normal,
the others partially transformed.

BIOLOGICAL LECTURES.

Plate VIII. — Onoclea Struthiopteris. a normal sporophyll. b partially transformed sporo-
phyll. c completely transformed sporophyll.

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