heredity--Haeckel's, for instance--or the metaphysical theory, but it is
hardly necessary. I do not accept in full any of them. Their authors, it
seems to me, have not worked along the lines of evolution, but have gone
further than was necessary into the fields of speculation. Darwin, in
his theory of Pangenesis, admitted this frankly, and yet he clung to the
idea with great tenacity. If we take the unicellular organisms which
multiply by division, we may see that heredity is simple. One
unicellular individual growing larger than is convenient, divides into
two. Each is like the other. It could hardly be different. Reproduction
by spores or buds is practically the same thing. The spores or buds are
minute particles of the parent organism. When it comes to the
coalescence of the germ and sperm elements from two organisms, the
phenomena become more complicated, and it is still more so as the animal
rises in the scale of creation; but I believe the processes of organic
evolution have gone on so slowly that the sexual cells have acquired the
power to transmit the whole organism without the necessity of the
germ-plasm being continued from parent to offspring indefinitely, and
also without the aid of pangenesis.
The egg has acquired a tendency to develop in a certain direction. Just
how we cannot tell, further than to say that it was probably the result
of variation first and natural selection selecting out those variations
most suitable. It is this tendency to vary that gives rise to many of
the phenomena of heredity. The subject is, for the present, beyond our
power to settle satisfactorily, and so hypotheses must be resorted to.
The sexual cells, comparatively simple in anatomical structure, must be
highly complex in their molecular structure; and the more highly evolved
the organism, the more complex becomes this molecular structure. If it
were possible to study this molecular structure we should be able to
understand the whole subject far better than is possible now. But this
is not possible, and there is little hope that we shall ever be able to
accomplish it.
HEREDITY AND THE EDUCATION OF CHILDREN.--The next question which comes
up for consideration is that of the education of children and its
relation to heredity. This brings us at once to the problem as to
whether acquired characters are transmitted to offspring or not. If
acquired characters are transmitted, the relation of heredity to
education must be very close and important. If acquired characters are
not inherited, then heredity and education have a very different
relation. That acquired characters are transmitted has long been
believed. It was the belief of Lamarck. He tried to explain the
structure of the organism by this principle. The illustration of the
long neck of the giraffe is familiar to every one. It originated by the
constant stretching of this part to obtain food from the trees. In times
of scarcity, he had to exert himself in this way still more to reach the
higher branches. The young of the giraffe had longer necks than their
parents because of the efforts of the latter in this way. So the keen
sight of birds, it was argued, was acquired in the same manner. The hawk
had to exercise his eyes most vigorously to discern his prey at a
distance, and his offspring inherited this keenness of sight acquired by
the exercise of his ancestors.
Darwin believed that the effects of the exercise of any part were
transmitted. He says: "We may feel assured that the inherited effects of
the use and disuse of parts will have done much in the same direction
with natural selection in modifying man's structure of body."
We may say that this belief has been held by the common people,
uneducated in science. They not unfrequently get at truths in a rude way
long before the scientists do. Many parents tell us their children are
strongly influenced by some particular occupation of the mother during
pregnancy. So strong is this belief, that many mothers are in our times
trying to influence the character of their unborn children by special
modes of life, by cultivating music or art, or science, in order to give
the child a love for these pursuits.
It is by Herbert Spencer that this has been most ably presented. Indeed,
he holds that there is no explanation of evolution without the
transmission of the effects of the use and disuse of parts. His words
are: "If there has been no transmission of acquired character there has
been no evolution."
He also says: "If we go back to the genesis of the human type from some
lower type of primates, we see that while the little toe has ceased to
be of any use for climbing purposes, it has not come into any
considerable use for walking or running. It is manifest that the great
toes have been immensely developed since there took place the change
from arboreal to terrestrial habits. A study of the mechanism of walking
shows why this has happened. Stability requires that the line of
direction--the vertical line, let fall from the center of gravity--shall
fall within the base, and the walking shall be brought at each step
within the area of support, or so near that any tendency to fall may be
checked at the next step. A necessary result is that _if_ at each step
the chief stress of support is thrown on the outer side of the foot, the
body must be swayed so that the line of direction may fall within the
outside of the foot, or close to it; and when the next step is taken it
must be similarly swayed in an opposite direction, so that the outer
side of the foot may bear the weight. That is to say, the body must
oscillate from side to side, or waddle. The movement of the duck when
walking shows what happens when the points of support are far apart.
This kind of movement conflicts with efficient locomotion. There is a
waste of muscular energy in making these lateral movements, and they are
at variance with the forward movement. We may infer, then, that the
developing man profited by throwing the stress as much as possible on
the inner side of the feet, and was especially led to do this when going
fast, which enabled him to abridge the oscillations, as indeed we see it
now in the drunken man. Then there was thrown a continually increasing
stress upon the inner digits as they progressively developed from the
efforts of use, until now the inner digits, so large compared with the
outer, bear the greater part of the weight, and being relatively near
one another render needless any swaying of the body from side to side in
walking. But what has meanwhile happened to the outer digits? Evidently
as fast as the great toes have come more and more into play and the
small ones have gone more and more out of play, dwindling for--how long
shall we say?--perhaps 100,000 years." In other and simpler words, the
great toe of man has wonderfully developed since he began to walk
upright. This has been from greater use, and the transmission of the
effects of this use to offspring. The small toe has decreased in size
proportionately. This we can reasonably infer has been the result of
disuse, the effects of which were also transmitted to offspring.
A still more remarkable illustration of the effects of use and disuse is
seen in the sense of touch in different parts of the body. Prof. Weber,
in his laboratory for experimental psychology, has worked out this
difference most minutely. He finds that by taking a pair of compasses,
the points of which are less than one-twelfth of an inch apart, the end
of the forefinger is not able to distinguish more than one point. Going
to the middle of the back we have the least discriminating power in the
skin, for the points must be separated two and one half inches before
the nerves can decide that there are two. Any one may test this on
himself. Between these extremes we have many differences. The end of
the nose has four times as great power of discrimination as the
forehead. When we come to the tip of the tongue, we find it far excels
any part of the body in its power of tactual discrimination, it being
twice that of the forefinger. In every case we find there is greatest
delicacy of touch in those parts where this sense has been most
exercised. The tongue is being constantly exercised on our food, on the
roof of the mouth, the teeth, etc. It is rarely idle. There is in man no
advantage for his survival, Mr. Spencer asserts, by having such a
sensitive tongue. He could get on just as well without it. He regards it
as a case where the exercise of a function has exalted it remarkably,
and this exaltation has been transmitted to offspring. Natural
selection, he thinks, is not sufficient to account for it. Natural
selection only preserves those characters which will give their
possessor some advantage in the struggle for existence.
Still another argument is drawn from the whale. This monster once lived,
it is believed, partly on land, probably on low land near water, and
must have been smaller than now. It had hind legs; but since it has
lived continuously in the water its tail has so developed as to make a
far better organ of locomotion, and the legs have dwindled from disuse,
so that now there is only a remnant left, and this is hidden beneath
the skin. The tail has become more efficient from use, and this has been
transmitted so that all whales are born with well developed tails. The
legs have dwindled for want of use until they have almost disappeared;
and this effect of disuse has also been transmitted to offspring.
Another illustration is furnished by Havelock Charles, an English
surgeon, who has spent much time among the Punjab tribes in India, and
studied them anthropologically. His account is given in "The Journal of
Anatomy," in a paper on the structure of the skeletons of these people.
It appears they have facets on the bones, fitting them for the sitting
posture. These do not develop after birth, but are seen in the fetus. It
seems hardly possible that these facets could have any other origin
except by transmission after being acquired by ages of use of sitting
posture.
Another argument is drawn from the coadaptation of parts. We know that
the male sheep, likewise the goat, the stag, and the males of many other
animals, have large horns. They are supposed to be useful in fighting
with rivals in order to secure as large a number of females as possible.
Now these large horns require at the same time a greater development of
the bones of the head to hold them, also larger and stronger vertebrae of
the neck and back, and larger muscles of these parts to maintain and
use them effectively. In other words, there must be coadaptation of all
the parts, otherwise these larger horns would be an incumbrance and
useless. Now, if we accept the theory of the inheritance of acquired
characters, this is all simple. The use of the head in butting against
other males exercises all these parts simultaneously, and they develop
equally and at the same time. If, however, inheritance has no part in
the matter, then we must fall back on variation in the germ-plasm and
natural selection for an explanation; but it is difficult or, as Spencer
says, impossible to conceive of variation producing large and heavy
horns on these animals and at the same time coadaptation of all the
other parts to hold and use them. Sometimes coadaptation does not take
place, as in the common brook crab, familiar to every country boy. Its
foreclaws or fingers are out of all proportion to the rest of the leg,
and its awkwardness is well known. The lobster is another case. Even in
human beings we have instances of non-coadaptation, as where the head
and brain are out of proportion to the size of the body, or the reverse.
I need not multiply instances.
Now, if acquired characters are transmitted, any system of training
which exists for a considerable time must necessarily appear in the
structure of the body and in the character. If the training is not in
accord with the laws of evolution, it causes the race to deviate from
the true line of progress, and by just so much hinder advancement. If,
on the other hand, our systems of education conform to correct
principles, progress is advanced by them.
Quite recently an entirely new theory has grown up, opposed to
Lamarckianism, and the theory of the transmission of acquired
characters. It has been before the world little more than a decade and
has made remarkable progress, though it is too soon to say it has been
established beyond dispute. Prof. Weismann, its author, is well equipped
as a biologist to maintain and defend it. I have already stated briefly
his theory of heredity, namely, that the germ-plasm is continuous from
parent to offspring. This necessitates a remodeling of commonly accepted
views, an entire giving up of the Lamarckian belief that use and disuse
have their effect on progeny. If the germ-plasm continues from one
generation to another, then it must already have been formed, or at
least provided for, even before the birth of the parents. They may
modify it, through growth and nutrition, but not through exercise of any
function. Prof. Weismann went at the demonstration of his views in a
thoroughly scientific way by the making of experiments on living animals
and the collection of facts. From his experiments it is now pretty well
established that wounds and injuries, which he considers to be acquired
characters, are not transmitted. No matter for how many generations you
cut off the tails of dogs, cats, horses or sheep, the effects of this
removal do not appear in the progeny. Most parents have some mark on the
body, received in early life, some cut or bruise, some scratch, but
their children do not inherit them. The famous experiment of cutting off
the tails of mice, for generation after generation, and then breeding
from them was one of Weismann's methods of substantiating the theory
that acquired character is not inherited. The offspring of these
mutilated mice had as long tails as if those of their parents had not
been removed. The explanation is, the germ-plasm was not in any way
affected by the bodily mutilation. The practice of the Flathead Indian
is another case. The children of parents whose heads have been
artificially flattened are not affected by it. The small feet of Chinese
women, made so by binding them and preventing their growth, may also be
mentioned.
INTELLECTUAL ACQUIREMENTS.--Not to depend on such evidence, however, he
adduces that of a very different character, namely, the non-transmission
of intellectual acquirements. Language is an example. Although human
beings have been communicating their thoughts to each other from very
ancient times by speech, yet every child has to learn how to do this
for itself. No matter how many languages the parents master, their
children have to go over all the ground the parents did, make all the
toil and effort to learn to speak. The children of the most gifted
linguists, if brought up without coming in contact with those who can
teach them to talk, will never learn a single word. There are, it is
claimed, a few cases on record of children who never acquired their
natural tongue because they had lived among animals and not among human
beings. They learned to make the same vocal sounds the animals did, no
more. The environment in this case was everything, the parental
acquirements nothing.
Music, like language, is also an acquired character, and it is probably
not transmitted. Our musical geniuses are not the children of great
musicians, but in most cases the reverse. They seem to spring into
existence from lowly sources, or at least from parents whose advantages
for a musical education have been very limited, though generally they
have had good health, and a climatic environment of a favorable kind.
Great musical talent usually dies out in any family in a few
generations, no matter how much it is cultivated, or, if it does not die
out entirely, it becomes mediocre; and yet the opportunities of the
children of great musicians, and the ambition of their parents for its
culture, are usually very favorable.
INSTINCT.--In accepting the theory of the non-transmission of acquired
characters, it becomes necessary to give up prevailing views of the
origin of instinct. According to the old belief it was a gift of God,
and not acquired by any effort on the part of its possessor. In speaking
of the instinct of bees, Sidney Smith says: "_Providence has done it._
There are the bees, there is the comb, and the honey, get rid of it or
find some other explanation if you can."
The early evolutionists changed all this, and made instinct the
inheritance of an oft-repeated act. The young kitten, as soon as old
enough, hunts for a mouse and catches it without any training. The sight
of the mouse acts on its nervous system in such a way as to compel it to
creep up softly, jump on it, toy and play with it, and finally kill and
eat it. It would have required long practice on the part of its
ancestors before so wonderful a character could have become fixed. The
same is true of the setter dog.
The new view is, that instincts arise from variations in the germ-plasm.
The union of the germ elements of two individuals causes it to vary more
or less from either parent. These variations will be favorable and
unfavorable. The unfavorable ones will produce offspring handicapped in
the struggle for life and they will disappear. The favorable variations
will produce descendants possessing advantages for survival and leave
numerous offspring.
It is not easy to accept this view, but I think there are some facts
that support it. I will advance a few. The hive of the honey-bee
contains three kinds of insects: the queen, the drones or males, and the
workers. The queen makes her nuptial flight but once in a life-time, and
does it from instinct. How can an instinct like this have been acquired
by being performed but once? The drones are derived from unfertilized
eggs; yet their instincts are those of the male, not of the female. As
they have no male ancestors, it seems probable there was in the
germ-plasm of some queen bee, at a time far back, some change which
allowed unfertilized eggs to produce males.
The workers are all females, not fully developed sexually on account of
a diet with too small a proportion of nitrogenous food and containing so
large a proportion of the hydrocarbons. They inherit from the mother, or
rather from the germ-plasm, the instinct to gather honey, yet neither
their male nor female ancestors ever gathered any honey in their lives,
nor have they for ages. Far back in antiquity the queen, no doubt, did
gather honey, but the disuse of this instinct has not caused it to
disappear in the working bee, as it should have done according to the
Lamarckian theory of disuse causing decay of function. Is there any way
to account for this, except on the theory that the germ-plasm produces
working bees as well as the other kinds, irrespective of the habits of
the queen? Her character in this respect is fixed and does not change.
Is it unreasonable to think that some time in the past, in some queen
bee, was formed a germ-plasm capable of producing three varieties, and
that there was such an advantage in it for survival, that it has been
continued ever since by natural selection? Queens not able to do this
have not been selected, left no offspring, and thus the perfection of
the stock has been assured.
One more case. Some years ago, when interested in agricultural
entomology, I made a study of the so-called seventeen-year locust.
Noting the wonderful precision with which the female cuts into a soft
twig of a tree and lays its eggs in two rows, the thought was suggested
to me, how can an instinct, used only a few hours, once in seventeen
years, be acquired by exercise and persist in the offspring seventeen
years later? Weismann's theory of the origin of instinct from favorable
variations in the germ-plasm offers, it seems to me, a rational
explanation.
I do not need to extend illustrations which abound in the insect world,
especially among the ants, which furnish cases of coadaptation that
cannot be transmitted, as they do not propagate, so I will not mention
them here.
Now, if acquired characters _are not_ transmitted to offspring, how
should these facts affect our methods of educating children?
One advantage will be evident, I think, to all. Erroneous systems of
training, which do not injure the health, will not appear through
heredity in the offspring of parents thus wrongly trained, except as a
result of environment. That is to say, the injury does not become
congenital--will not be in the blood--and, consequently, it will be less
difficult to eradicate it and to introduce better systems. This may be
considered an advantage. But it is not all. If heredity takes place only
through the germ-plasm, then it seems to me that whatever promotes a
knowledge of how to maintain it in a high degree of health, and how to
favor more perfectly natural selection, are subjects with which our
educators may busy themselves far more than they do. That is to say, the
study of biology, of life--of the laws of human growth and development,
and of evolution, will become, more and more, important factors in our
school curriculum. We can hardly imagine how much our common every-day
life has been aided by even the slight knowledge of mathematics gained
by an acquaintance with addition, subtraction, multiplication and
division. By it we are able to keep our little accounts correctly, and
neither cheat our creditors nor be cheated by them. Could we not by a
knowledge of the laws of evolution, and also the laws of growth and
development, keep our larger account with nature in a far better
condition? Could we not keep ourselves from being cheated out of our
health and happiness, and also do something to put an end to physical,
intellectual and moral deterioration which threatens so many families
and even races? It seems to me that the time is not far distant when
these studies will be quite as much attended to as the not unimportant
ones of arithmetic and grammar.
KNOWLEDGE OF HEREDITY.--Whatever doctrine of heredity prevails, however,
one thing is certain, some knowledge of the subject will be very useful
to those who have in care the training of children. To them, often more
than to the parent, is entrusted the task of developing the character
and the individuality of the child. Can he do this well if he knows
nothing of what the bent of the child's genius from ancestral influence
is? I doubt very much if any of us realize how important it is that this
individuality should have its proper share of attention. As the
evolution of society goes on, more and more must there be
differentiation of our various activities. If every boy and every girl
can be educated so that to a considerable extent they can follow the
bent of their genius, _whenever that bent is a normal one_, will not the
available intellectual and moral energy of society be considerably
augmented? If you educate a boy which nature intended for a blacksmith
for a preacher, has not the world lost something? Educate another for a
blacksmith who should have been a preacher, is there not also a great
loss? There are a few children who will come out all right, no matter
how much they are schooled, or whether they have any schooling, so well
have they been born, but with the majority this is not the case. Now it
seems to me that the teacher who knows the natures of his pupils, and
something of their ancestors', can direct their energies more
satisfactorily than the one who does not. If there are hereditary
defects of intellect or morals, he can more easily correct them. If
there are ancestral tendencies to disease through imperfections of
certain organs, for instance, the lungs or the brain, he can often put
the child on such a course of physical culture or mental training as to
lift it above danger, so that it may go through life a useful person
instead of a feeble one or a lunatic. Even the tendency to crime might
be averted.