The sex of the egg is optional. The choice rests with the mother, who is
guided by considerations of space and, according to the accommodation
at her disposal, which is frequently fortuitous and incapable of
modification, places a female in this cell and a male in that, so that
both may have a dwelling of a size suited to their unequal development.
This is the unimpeachable evidence of the numerous and varied facts
which I have set forth. People unfamiliar with insect anatomy--the
public for whom I write--would probably give the following explanation
of this marvellous prerogative of the Bee: the mother has at her
disposal a certain number of eggs, some of which are irrevocably female
and the others irrevocably male: she is able to pick out of either group
the one which she wants at the actual moment; and her choice is decided
by the holding capacity of the cell that has to be stocked. Everything
would then be limited to a judicious selection from the heap of eggs.
Should this idea occur to him, the reader must hasten to reject it.
Nothing could be more false, as the merest reference to anatomy will
show. The female reproductive apparatus of the Hymenoptera consists
generally of six ovarian tubes, something like glove-fingers, divided
into bunches of three and ending in a common canal, the oviduct, which
carries the eggs outside. Each of these glove-fingers is fairly wide
at the base, but tapers sharply towards the tip, which is closed.
It contains, arranged in a row, one after the other, like beads on a
string, a certain number of eggs, five or six for instance, of which the
lower ones are more or less developed, the middle ones half-way towards
maturity, and the upper ones very rudimentary. Every stage of evolution
is here represented, distributed regularly from bottom to top, from the
verge of maturity to the vague outlines of the embryo. The sheath clasps
its string of ovules so closely that any inversion of the order is
impossible. Besides, an inversion would result in a gross absurdity: the
replacing of a riper egg by another in an earlier stage of development.
Therefore, in each ovarian tube, in each glove-finger, the emergence of
the eggs occurs according to the order governing their arrangement in
the common sheath; and any other sequence is absolutely impossible.
Moreover, at the nesting period, the six ovarian sheaths, one by one and
each in its turn, have at their base an egg which in a very short time
swells enormously. Some hours or even a day before the laying, that egg
by itself represents or even exceeds in bulk the whole of the ovigenous
apparatus. This is the egg which is on the point of being laid. It is
about to descend into the oviduct, in its proper order, at its proper
time; and the mother has no power to make another take its place. It is
this egg, necessarily this egg and no other, that will presently be laid
upon the provisions, whether these be a mess of honey or a live prey; it
alone is ripe, it alone is at the entrance to the oviduct; none of the
others, since they are farther back in the row and not at the right
stage of development, can be substituted at this crisis. Its birth is
inevitable.
What will it yield, a male or a female? No lodging has been prepared,
no food collected for it; and yet both food and lodging have to be in
keeping with the sex that will proceed from it. And here is a much more
puzzling condition: the sex of that egg, whose advent is predestined,
has to correspond with the space which the mother happens to have found
for a cell. There is therefore no room for hesitation, strange though
the statement may appear: the egg, as it descends from its ovarian tube,
has no determined sex. It is perhaps during the few hours of its rapid
development at the base of its ovarian sheath, it is perhaps on its
passage through the oviduct that it receives, at the mother's pleasure,
the final impress that will produce, to match the cradle which it has to
fill, either a female or a male.
Thereupon the following question presents itself. Let us admit that,
when the normal conditions remain, a laying would have yielded m females
and n males. Then, if my conclusions are correct, it must be in the
mother's power, when the conditions are different, to take from the m
group and increase the n group to the same extent; it must be possible
for her laying to be represented as m-1, m-2, m-3, etc. females and by
n+1, n+2, n+3, etc. males, the sum of m+n remaining constant, but one of
the sexes being partly permuted into the other. The ultimate conclusion
even cannot be disregarded: we must admit a set of eggs represented
by m-m, or zero, females and of n+m males, one of the sexes being
completely replaced by the other. Conversely, it must be possible for
the feminine series to be augmented from the masculine series to the
extent of absorbing it entirely. It was to solve this question and some
others connected with it that I undertook, for the second time, to rear
the Three-horned Osmia in my study.
The problem on this occasion is a more delicate one; but I am
also better-equipped. My apparatus consists of two small, closed
packing-cases, with the front side of each pierced with forty holes,
in which I can insert my glass tubes and keep them in a horizontal
position. I thus obtain for the Bees the darkness and mystery which suit
their work and for myself the power of withdrawing from my hive, at any
time, any tube that I wish, with the Osmia inside, so as to carry it
to the light and follow, if need be with the aid of the lens, the
operations of the busy worker. My investigations, however frequent and
minute, in no way hinder the peaceable Bee, who remains absorbed in her
maternal duties.
I mark a plentiful number of my guests with a variety of dots on the
thorax, which enables me to follow any one Osmia from the beginning
to the end of her laying. The tubes and their respective holes are
numbered; a list, always lying open on my desk, enables me to note from
day to day, sometimes from hour to hour, what happens in each tube and
particularly the actions of the Osmiae whose backs bear distinguishing
marks. As soon as one tube is filled, I replace it by another. Moreover,
I have scattered in front of either hive a few handfuls of empty
Snail-shells, specially chosen for the object which I have in view.
Reasons which I will explain later led me to prefer the shells of Helix
caespitum. Each of the shells, as and when stocked, received the date
of the laying and the alphabetical sign corresponding with the Osmia to
whom it belonged. In this way, I spent five or six weeks in continual
observation. To succeed in an enquiry, the first and foremost condition
is patience. This condition I fulfilled; and it was rewarded with the
success which I was justified in expecting.
The tubes employed are of two kinds. The first, which are cylindrical
and of the same width throughout, will be of use for confirming the
facts observed in the first year of my experiments in indoor rearing.
The others, the majority, consist of two cylinders which are of very
different diameters, set end to end. The front cylinder, the one which
projects a little way outside the hive and forms the entrance-hole,
varies in width between 8 and 12 millimetres. (Between.312 to .468
inch.--Translator's Note.) The second, the back one, contained
entirely within my packing-case, is closed at its far end and is 5 to 6
millimetres (.195 to.234 inch.--Translator's Note.) in diameter. Each of
the two parts of the double-galleried tunnel, one narrow and one wide,
measures at most a decimetre (3.9 inches.--Translator's Note.) in
length. I thought it advisable to have these short tubes, as the Osmia
is thus compelled to select different lodgings, each of them being
insufficient in itself to accommodate the total laying. In this way I
shall obtain a greater variety in the distribution of the sexes. Lastly,
at the mouth of each tube, which projects slightly outside the case,
there is a little paper tongue, forming a sort of perch on which the
Osmia alights on her arrival and giving easy access to the house. With
these facilities, the swarm colonized fifty-two double-galleried tubes,
thirty-seven cylindrical tubes, seventy-eight Snail-shells and a few old
nests of the Mason-bee of the Shrubs. From this rich mine of material I
will take what I want to prove my case.
Every series, even when incomplete, begins with females and ends with
males. To this rule I have not yet found an exception, at least in
galleries of normal diameter. In each new abode, the mother busies
herself first of all with the more important sex. Bearing this point
in mind, would it be possible for me, by manoeuvring, to obtain an
inversion of this order and make the laying begin with males? I
think so, from the results already ascertained and the irresistible
conclusions to be drawn from them. The double-galleried tubes are
installed in order to put my conjectures to the proof.
The back gallery, 5 or 6 millimetres (.195 to.234 inch.--Translator's
Note.) wide, is too narrow to serve as a lodging for normally developed
females. If, therefore, the Osmia, who is very economical of her space,
wishes to occupy them, she will be obliged to establish males there.
And her laying must necessarily begin here, because this corner is
the rear-most part of the tube. The foremost gallery is wide, with an
entrance-door on the front of the hive. Here, finding the conditions to
which she is accustomed, the mother will go on with her laying in the
order which she prefers.
Let us now see what has happened. Of the fifty-two double galleried
tubes, about a third did not have their narrow passage colonized. The
Osmia closed its aperture communicating with the large passage; and the
latter alone received the eggs. This waste of space was inevitable.
The female Osmiae, though nearly always larger than the males, present
marked differences among one another: some are bigger, some are smaller.
I had to adjust the width of the narrow galleries to Bees of average
dimensions. It may happen therefore that a gallery is too small to admit
the large-sized mothers to whom chance allots it. When the Osmia is
unable to enter the tube, obviously she will not colonize it. She then
closes the entrance to this space which she cannot use and does her
laying beyond it, in the wide tube. Had I tried to avoid these useless
apparatus by choosing tubes of larger calibre, I should have encountered
another drawback: the medium-sized mothers, finding themselves almost
comfortable, would have decided to lodge females there. I had to be
prepared for it: as each mother selected her house at will and as I was
unable to interfere in her choice, a narrow tube would be colonized or
not, according as the Osmia who owned it was or was not able to make her
way inside.
There remain some forty pairs of tubes with both galleries colonized. In
these there are two things to take into consideration. The narrow
rear tubes of 5 or 5 1/2 millimetres (.195 to.214 inch.--Translator's
Note.)--and these are the most numerous--contain males and males only,
but in short series, between one and five. The mother is here so much
hampered in her work that they are rarely occupied from end to end; the
Osmia seems in a hurry to leave them and to go and colonize the front
tube, whose ample space will leave her the liberty of movement necessary
for her operations. The other rear tubes, the minority, whose diameter
is about 6 millimetres (.234 inch.--Translator's Note.), contain
sometimes only females and sometimes females at the back and males
towards the opening. One can see that a tube a trifle wider and a mother
slightly smaller would account for this difference in the results.
Nevertheless, as the necessary space for a female is barely provided
in this case, we see that the mother avoids as far as she can a two-sex
arrangement beginning with males and that she adopts it only in the
last extremity. Finally, whatever the contents of the small tube may
be, those of the large one, following upon it, never vary and consist of
females at the back and males in front.
Though incomplete, because of circumstances very difficult to control,
the result of the experiment is none the less very striking. Twenty-five
apparatus contain only males in their narrow gallery, in numbers varying
from a minimum of one to a maximum of five. After these comes the colony
of the large gallery, beginning with females and ending with males. And
the layings in these apparatus do not always belong to late summer or
even to the intermediate period: a few small tubes contain the earliest
eggs of the Osmiae. A couple of Osmiae, more forward than the others,
set to work on the 23rd of April. Both of them started their laying by
placing males in the narrow tubes. The meagre supply of provisions was
enough in itself to show the sex, which proved later to be in accordance
with my anticipations. We see then that, by my artifices, the whole
swarm starts with the converse of the normal order. This inversion is
continued, at no matter what period, from the beginning to the end of
the operations. The series which, according to rule, would begin with
females now begins with males. Once the larger gallery is reached, the
laying is pursued in the usual order.
We have advanced one step and that no small one: we have seen that
the Osmia, when circumstances require it, is capable of reversing the
sequence of the sexes. Would it be possible, provided that the tube were
long enough, to obtain a complete inversion, in which the entire series
of the males should occupy the narrow gallery at the back and the entire
series of the females the roomy gallery in front? I think not; and I
will tell you why.
Long and narrow cylinders are by no means to the Osmia's taste, not
because of their narrowness but because of their length. Remember that
for each load of honey brought the worker is obliged to move backwards
twice. She enters, head first, to begin by disgorging the honey-syrup
from her crop. Unable to turn in a passage which she blocks entirely,
she goes out backwards, crawling rather than walking, a laborious
performance on the polished surface of the glass and a performance
which, with any other surface, would still be very awkward, as the wings
are bound to rub against the wall with their free end and are liable to
get rumpled or bent. She goes out backwards, reaches the outside, turns
round and goes in again, but this time the opposite way, so as to brush
off the load of pollen from her abdomen on to the heap. If the gallery
is at all long, this crawling backwards becomes troublesome after a
time; and the Osmia soon abandons a passage that is too small to allow
of free movement. I have said that the narrow tubes of my apparatus
are, for the most part, only very incompletely colonized. The Bee, after
lodging a small number of males in them, hastens to leave them. In the
wide front gallery, she can stay where she is and still be able to turn
round easily for her different manipulations; she will avoid those two
long journeys backwards, which are so exhausting and so bad for her
wings.
Another reason no doubt prompts her not to make too great a use of the
narrow passage, in which she would establish males, followed by females
in the part where the gallery widens. The males have to leave their
cells a couple of weeks or more before the females. If they occupy the
back of the house, they will die prisoners or else they will overturn
everything on their way out. This risk is avoided by the order which the
Osmia adopts.
In my tubes with their unusual arrangement, the mother might well find
the dilemma perplexing: there is the narrowness of the space at her
disposal and there is the emergence later on. In the narrow tubes, the
width is insufficient for the females; on the other hand, if she lodges
males there, they are liable to perish, since they will be prevented
from issuing at the proper moment. This would perhaps explain the
mother's hesitation and her obstinacy in settling females in some of my
apparatus which looked as if they could suit none but males.
A suspicion occurs to me, a suspicion aroused by my attentive
examination of the narrow tubes. All, whatever the number of their
inmates, are carefully plugged at the opening, just as separate tubes
would be. It might therefore be the case that the narrow gallery at the
back was looked upon by the Osmia not as the prolongation of the large
front gallery, but as an independent tube. The facility with which
the worker turns as soon as she reaches the wide tube, her liberty of
action, which is now as great as in a doorway communicating with the
outer air, might well be misleading and cause the Osmia to treat the
narrow passage at the back as though the wide passage in front did not
exist. This would account for the placing of the female in the large
tube above the males in the small tube, an arrangement contrary to her
custom.
I will not undertake to decide whether the mother really appreciates the
danger of my snares, or whether she makes a mistake in considering
only the space at her disposal and beginning with males. At any rate,
I perceive in her a tendency to deviate as little as possible from the
order which safeguards the emergence of the two sexes. This tendency is
demonstrated by her repugnance to colonizing my narrow tubes with long
series of males. However, so far as we are concerned, it does not matter
much what passes at such times in the Osmia's little brain. Enough for
us to know that she dislikes narrow and long tubes, not because they are
narrow, but because they are at the same time long.
And, in fact, she does very well with a short tube of the same diameter.
Such are the cells in the old nests of the Mason-bee of the Shrubs
and the empty shells of the Garden Snail. With the short tube, the two
disadvantages of the long tube are avoided. She has very little of that
crawling backwards to do when she has a Snail-shell for the home of
her eggs and scarcely any when the home is the cell of the Mason-bee.
Moreover, as the stack of cocoons numbers two or three at most, the
deliverance will be exempt from the difficulties attached to a long
series. To persuade the Osmia to nidify in a single tube long enough to
receive the whole of her laying and at the same time narrow enough
to leave her only just the possibility of admittance appears to me
a project without the slightest chance of success: the Bee would
stubbornly refuse such a dwelling or would content herself with
entrusting only a very small portion of her eggs to it. On the other
hand, with narrow but short cavities, success, without being easy,
seems to me at least quite possible. Guided by these considerations,
I embarked upon the most arduous part of my problem: to obtain the
complete or almost complete permutation of one sex with the other;
to produce a laying consisting only of males by offering the mother a
series of lodgings suited only to males.
Let us in the first place consult the old nests of the Mason-bee of the
Shrubs. I have said that these mortar spheroids, pierced all over
with little cylindrical cavities, are adopted pretty eagerly by the
Three-horned Osmia, who colonizes them before my eyes with females in
the deep cells and males in the shallow cells. That is how things go
when the old nest remains in its natural state. With a grater, however,
I scrape the outside of another nest so as to reduce the depth of
the cavities to some ten millimetres. (About two-fifths of an
inch.--Translator's Note.) This leaves in each cell just room for one
cocoon, surmounted by the closing stopper. Of the fourteen cavities in
the nests, I leave two intact, measuring fifteen millimetres in depth.
(.585 inch.--Translator's Note.) Nothing could be more striking than the
result of this experiment, made in the first year of my home rearing.
The twelve cavities whose depth had been reduced all received males; the
two cavities left untouched received females.
A year passes and I repeat the experiment with a nest of fifteen cells;
but this time all the cells are reduced to the minimum depth with the
grater. Well, the fifteen cells, from first to last, are occupied by
males. It must be quite understood that, in each case, all the offspring
belonged to one mother, marked with her distinguishing spot and kept
in sight as long as her laying lasted. He would indeed be difficult to
please who refused to bow before the results of these two experiments.
If, however, he is not yet convinced, here is something to remove his
last doubts.
The Three-horned Osmia often settles her family in old shells,
especially those of the Common Snail (Helix aspersa), who is so common
under the stone-heaps and in the crevices of the little unmortared walls
that support our terraces. In this species, the spiral is wide open, so
that the Osmia, penetrating as far down as the helical passage permits,
finds, immediately above the point which is too narrow to pass, the
space necessary for the cell of a female. This cell is succeeded by
others, wider still, always for females, arranged in a line in the same
way as in a straight tube. In the last whorl of the spiral, the diameter
would be too great for a single row. Then longitudinal partitions are
added to the transverse partitions, the whole resulting in cells of
unequal dimensions in which males predominate, mixed with a few females
in the lower storeys. The sequence of the sexes is therefore what it
would be in a straight tube and especially in a tube with a wide bore,
where the partitioning is complicated by subdivisions on the same level.
A single Snail-shell contains room for six or eight cells. A large,
rough earthen stopper finishes the nest at the entrance to the shell.
As a dwelling of this sort could show us nothing new, I chose for my
swarm the Garden Snail (Helix caespitum), whose shell, shaped like a
small, swollen Ammonite, widens by slow degrees, the diameter of the
usable portion, right up to the mouth, being hardly greater than that
required by a male Osmia-cocoon. Moreover, the widest part, in which
a female might find room, has to receive a thick stopping-plug, below
which there will often be a free space. Under all these conditions, the
house will hardly suit any but males arranged one after the other.
The collection of shells placed at the foot of each hive includes
specimens of different sizes. The smallest are 18 millimetres (.7
inch.--Translator's Note.) in diameter and the largest 24 millimetres
(.936 inch.--Translator's Note.) There is room for two cocoons, or three
at most, according to their dimensions.
Now these shells were used by my visitors without any hesitation,
perhaps even with more eagerness than the glass tubes, whose slippery
sides might easily be a little annoying to the Bee. Some of them were
occupied on the first few days of the laying; and the Osmia who
had started with a home of this sort would pass next to a second
Snail-shell, in the immediate neighbourhood of the first, to a third, a
fourth and others still, always close to one another, until her ovaries
were emptied. The whole family of one mother would thus be lodged in
Snail-shells which were duly marked with the date of the laying and a
description of the worker. The faithful adherents of the Snail-shell
were in the minority. The greater number left the tubes to come to
the shells and then went back from the shells to the tubes. All, after
filling the spiral staircase with two or three cells, closed the house
with a thick earthen stopper on a level with the opening. It was a long
and troublesome task, in which the Osmia displayed all her patience as
a mother and all her talents as a plasterer. There were even some who,
scrupulous to excess, carefully cemented the umbilicus, a hole which
seemed to inspire them with distrust as being able to give access to the
interior of the dwelling. It was a dangerous-looking cavity, which for
the greater safety of the family it was prudent to block up.
When the pupae are sufficiently matured, I proceed to examine
these elegant abodes. The contents fill me with joy: they fulfil my
anticipations to the letter. The great, the very great majority of the
cocoons turn out to be males; here and there, in the bigger cells, a
few rare females appear. The smallness of the space has almost done away
with the sixty-eight Snail-shells colonized. But, of this total number,
I must use only those series which received an entire laying and
were occupied by the same Osmia from the beginning to the end of
the egg-season. Here are a few examples, taken from among the most
conclusive.
From the 6th of May, when she started operations, to the 25th of
May, the date at which her laying ceased, the Osmia occupied seven
Snail-shells in succession. Her family consists of fourteen cocoons,
a number very near the average; and, of these fourteen cocoons, twelve
belong to males and only two to females. These occupy the seventh and
thirteenth places in chronological order.
Another, between the 9th and 27th of May, stocked six Snail-shells with
a family of thirteen, including ten males and three females. The places
occupied by the latter in the series were numbers 3, 4 and 5.
A third, between the 2nd and 29th of May, colonized eleven Snail-shells,
a prodigious task. This industrious one was also exceedingly prolific.
She supplied me with a family of twenty-six, the largest which I have
ever obtained from one Osmia. Well, this abnormal progeny consisted of
twenty-five males and one female, one alone, occupying place 17.
There is no need to go on, after this magnificent example, especially as
the other series would all, without exception, give us the same result.
Two facts are immediately obvious. The Osmia is able to reverse the
order of her laying and to start with a more or less long series of
males before producing any females. In the first case, the first female
appears as number 7; in the third, as number 17. There is something
better still; and this is the proposition which I was particularly
anxious to prove: the female sex can be permuted with the male sex and
can be permuted to the point of disappearing altogether. We see this
especially in the third case, where the presence of a solitary female
in a family of twenty-six is due to the somewhat larger diameter of the
corresponding Snail-shell and also, no doubt, to some mistake on the
mother's part, for the female cocoon, in a series of two, occupies the
upper storey, the one next to the orifice, an arrangement which the
Osmia appears to me to dislike.
This result throws so much light on one of the darkest corners of
biology that I must attempt to corroborate it by means of even more
conclusive experiments. I propose next year to give the Osmiae nothing
but Snail-shells for a lodging, picked out one by one, and rigorously
to deprive the swarm of any other retreat in which the laying could be
effected. Under these conditions, I ought to obtain nothing but males,
or nearly, for the whole swarm.
There would still remain the inverse permutation: to obtain only females
and no males, or very few. The first permutation makes the second seem
very probable, although I cannot as yet conceive a means of realizing
it. The only condition which I can regulate is the dimensions of the
home. When the rooms are small, the males abound and the females tend to
disappear. With generous quarters, the converse would not take place. I
should obtain females and afterwards an equal number of males, confined
in small cells which, in case of need, would be bounded by numerous
partitions. The factor of space does not enter into the question here.
What artifice can we then employ to provoke this second permutation? So
far, I can think of nothing that is worth attempting.
It is time to conclude. Leading a retired life, in the solitude of
a village, having quite enough to do with patiently and obscurely
ploughing my humble furrow, I know little about modern scientific views.
In my young days I had a passionate longing for books and found it
difficult to procure them; to-day, when I could almost have them if I
wanted, I am ceasing to wish for them. It is what usually happens as
life goes on. I do not therefore know what may have been done in the
direction whither this study of the sexes has led us. If I am stating
propositions that are really new or at least more comprehensive than the
propositions already known, my words will perhaps sound heretical. No
matter: as a simple translator of facts, I do not hesitate to make my
statement, being fully persuaded that time will turn my heresy into
orthodoxy. I will therefore recapitulate my conclusions.
Bees lay their eggs in series of first females and then males, when
the two sexes are of different sizes and demand an unequal quantity of
nourishment. When the two sexes are alike in size, the same sequence may
occur, but less regularly.
This dual arrangement disappears when the place chosen for the nest
is not large enough to contain the entire laying. We then see broken
layings, beginning with females and ending with males.
The egg, as it issues from the ovary, has not yet a fixed sex. The final
impress that produces the sex is given at the moment of laying or a
little before.
So as to be able to give each larva the amount of space and food that
suits it according as it is male or female, the mother can choose the
sex of the egg which she is about to lay. To meet the conditions of the
building, which is often the work of another or else a natural retreat
that admits of little or no alteration, she lays either a male egg or
a female egg as she pleases. The distribution of the sexes depends upon
herself. Should circumstances require it, the order of the laying can
be reversed and begin with males; lastly, the entire laying can contain
only one sex.
The same privilege is possessed by the predatory Hymenoptera, the Wasps,
at least by those in whom the two sexes are of a different size and
consequently require an amount of nourishment that is larger in the one
case than in the other. The mother must know the sex of the egg which
she is going to lay; she must be able to choose the sex of that egg so
that each larva may obtain its proper portion of food.
Generally speaking, when the sexes are of different sizes, every insect
that collects food and prepares or selects a dwelling for its offspring
must be able to choose the sex of the egg in order to satisfy without
mistake the conditions imposed upon it.
The question remains how this optional assessment of the sexes is
effected. I know absolutely nothing about it. If I should ever learn
anything about this delicate point, I shall owe it to some happy chance
for which I must wait, or rather watch, patiently. Towards the end of my
investigations, I heard of a German theory which relates to the Hive-bee
and comes from Dzierzon, the apiarist. (Johann Dzierzon, author of
"Theorie und Praxis des neuen Bienenfreundes."--Translator's Note.) If I
understand it aright, according to the very incomplete documents which I
have before me, the egg, as it issues from the ovary, is said already to
possess a sex, which is always the same; it is originally male; and it
becomes female by fertilization. The males are supposed to proceed from
non-fertilized eggs, the females from fertilized eggs. The Queen-bee
would thus lay female eggs or male eggs according as she fertilized them
or not while they were passing into her oviduct.
Coming from Germany, this theory cannot but inspire me with profound
distrust. As it has been given acceptance, with rash precipitancy, in
standard works, I will overcome my reluctance to devoting my attention
to Teutonic ideas and will submit it not to the test of argument, which
can always be met by an opposite argument, but to the unanswerable test
of facts.
For this optional fertilization, determining the sex, the mother's
organism requires a seminal reservoir which distils its drop of sperm
upon the egg contained in the oviduct and thus gives it a feminine
character, or else leaves it its original character, the male character,
by refusing it that baptism. This reservoir exists in the Hive-bee.
Do we find a similar organ in the other Hymenoptera, whether
honey-gatherers or hunters? The anatomical treatises are either silent
on this point or, without further enquiry, apply to the order as a whole
the data provided by the Hive-bee, however much she differs from the
mass of Hymenoptera owing to her social habits, her sterile workers and
especially her tremendous fertility, extending over so long a period.
I at first doubted the universal presence of this spermatic receptacle,
having failed to find it under my scalpel in my former investigations
into the anatomy of the Sphex-wasps and some other game-hunters. But
this organ is so delicate and so small that it very easily escapes the
eye, especially when our attention is not specially directed in search
of it; and, even when we are looking for it and it only, we do not
always succeed in discovering it. We have to find a globule attaining
in many cases hardly as much as a millimetre (About one-fiftieth of an
inch.--Translator's Note.) in diameter, a globule headed amidst a tangle
of air-ducts and fatty patches, of which it shares the colour, a dull
white. Then again, the merest slip of the forceps is enough to destroy
it. My first investigations, therefore, which concerned the reproductive
apparatus as a whole, might very well have allowed it to pass
unperceived.
In order to know the rights of the matter once and for all, as the
anatomical treatises taught me nothing, I once more fixed my microscope
on its stand and rearranged my old dissecting-tank, an ordinary tumbler
with a cork disk covered with black satin. This time, not without a
certain strain on my eyes, which are already growing tired, I succeeded
in finding the said organ in the Bembex-wasps, the Halicti (Cf.
Chapters 12 to 14 of the present volume.--Translator's Note.), the
Carpenter-bees, the Bumble-bees, the Andrenae (A species of Burrowing
Bees.--Translator's Note.) and the Megachiles. (Or Leaf-cutting Bees.
Cf. Chapter 8 of the present volume.--Translator's Note.) I failed in
the case of the Osmiae, the Chalicodomae and the Anthophorae. Is the
organ really absent? Or was there want of skill on my part? I
lean towards want of skill and admit that all the game-hunting and
honey-gathering Hymenoptera possess a seminal receptacle, which can be
recognized by its contents, a quantity of spiral spermatozoids whirling
and twisting on the slide of the microscope.
This organ once accepted, the German theory becomes applicable to all
the Bees and all the Wasps. When copulating, the female receives the
seminal fluid and holds it stored in her receptacle. From that moment,
the two procreating elements are present in the mother at one and the
same time: the female element, the ovule; and the male element, the
spermatozoid. At the egg-layer's will, the receptacle bestows a tiny
drop of its contents upon the matured ovule, when it reaches
the oviduct, and you have a female egg; or else it withholds its
spermatozoids and you have an egg that remains male, as it was at first.
I readily admit it: the theory is very simple, lucid and seductive. But
is it correct? That is another question.
One might begin by reproaching it with making a singular exception to
one of the most general rules. Which of us, casting his eyes over the
whole zoological progression, would dare to assert that the egg is
originally male and that it becomes female by fertilization? Do not the
two sexes both call for the assistance of the fertilizing element? If
there be one undoubted truth, it is certainly that. We are, it is true,
told very curious things about the Hive-bee. I will not discuss them:
this Bee stands too far outside the ordinary limits; and then the facts
asserted are far from being accepted by everybody. But the non-social
Bees and the predatory insects have nothing special about their laying.
Then why should they escape the common rule, which requires that every
living creature, male as well as female, should come from a fertilized
ovule? In its most solemn act, that of procreation, life is one and
uniform; what it does here it does there and there and everywhere. What!
The sporule of a scrap of moss requires an antherozoid before it is
fit to germinate; and the ovule of a Scolia, that proud huntress, can
dispense with the equivalent in order to hatch and produce a male? These
new-fangled theories seem to me to have very little value.
One might also bring forward the case of the Three-pronged Osmia, who
distributes the two sexes without any order in the hollow of her reed.
What singular whim is the mother obeying when, without decisive motive,
she opens her seminal phial at haphazard to anoint a female egg, or
else keeps it closed, also at haphazard, to allow a male egg to pass
unfertilized? I could imagine impregnation being given or withheld
for periods of some duration; but I cannot understand impregnation and
non-impregnation following upon each other anyhow, in any sort of order,
or rather with no order it all. The mother has just fertilized an egg.
Why should she refuse to fertilize the next, when neither the provisions
nor the lodgings differ in the smallest respect from the previous
provisions and lodgings? These capricious alternations, so unreasonable
and so exceedingly erratic, are scarcely appropriate to an act of such
importance.
But I promised not to argue and I find myself arguing. My reasoning is
too fine for dull wits. I will pass on and come to the brutal fact, the
real sledge-hammer blow.
Towards the end of the Bee's operations, in the first week of June, the
last acts of the Three-horned Osmia become so exceptionally interesting
that I made her the object of redoubled observation. The swarm at this
time is greatly reduced in numbers. I have still some thirty laggards,
who continue very busy, though their work is in vain. I see some very
conscientiously stopping up the entrance to a tube or a Snail-shell in
which they have laid nothing at all. Others are closing the home after
only building a few partitions, or even mere attempts at partitions.
Some are placing at the back of a new gallery a pinch of pollen which
will benefit nobody and then shutting up the house with an earthen
stopper as thick, as carefully made as though the safety of a family
depended on it. Born a worker, the Osmia must die working. When her
ovaries are exhausted, she spends the remainder of her strength on
useless works: partitions, plugs, pollen-heaps, all destined to be left
unemployed. The little animal machine cannot bring itself to be inactive
even when there is nothing more to be done. It goes on working so that
its last vibrations of energy may be used up in fruitless labour. I
commend these aberrations to the staunch supporters of reasoning-powers
in the animal.
Before coming to these useless tasks, my laggards have laid their last
eggs, of which I know the exact cells, the exact dates. These eggs, as
far as the microscopes can tell, differ in no respect from the others,
the older ones. They have the same dimensions, the same shape, the same
glossiness, the same look of freshness. Nor are their provisions in
any way peculiar, being very well suited to the males, who conclude the
laying. And yet these last eggs do not hatch: they wrinkle, fade and
wither on the pile of food. In one case, I count three or four sterile
eggs among the last lot laid; in another, I find two or only one.
Elsewhere in the swarm, fertile eggs have been laid right up to the end.
Those sterile eggs, stricken with death at the moment of their birth,
are too numerous to be ignored. Why do they not hatch like the other
eggs, which outwardly they resemble in every respect? They have received
the same attention from the mother and the same portion of food. The
searching microscope shows me nothing in them to explain the fatal
ending.
To the unprejudiced mind, the answer is obvious. Those eggs do not hatch
because they have not been fertilized. Any animal or vegetable egg that
had not received the life-giving impregnation would perish in the same
way. No other answer is possible. It is no use talking of the distant
period of the laying: eggs of the same period laid by other mothers,
eggs of the same date and likewise the final ones of a laying, are
perfectly fertile. Once more, they do not hatch because they were not
fertilized.
And why were they not fertilized? Because the seminal receptacle, so
tiny, so difficult to see that it sometimes escaped me despite all
my scrutiny, had exhausted its contents. The mothers in whom this
receptacle retained a remnant of sperm to the end had their last eggs as
fertile as the first; the others, whose seminal reservoir was exhausted
too soon, had their last-born stricken with death. All this seems to me
as clear as daylight.
If the unfertilized eggs perish without hatching, those which hatch and
produce males are therefore fertilized; and the German theory falls to
the ground.
Then what explanation shall I give of the wonderful facts which I have
set forth? Why, none, absolutely none. I do not explain facts, I relate
them. Growing daily more sceptical of the interpretations suggested to
me and more hesitating as to those which I may have to suggest myself,
the more I observe and experiment, the more clearly I see rising out of
the black mists of possibility an enormous note of interrogation.
Dear insects, my study of you has sustained me and continues to sustain
me in my heaviest trials. I must take leave of you for to-day. The ranks
are thinning around me and the long hopes have fled. Shall I be able to
speak to you again? (This is the closing paragraph of Volume 3 of the
"Souvenirs entomologiques," of which the author has lived to publish
seven more volumes, containing over 2,500 pages and nearly 850,000
words.--Translator's Note.)