The Faber Book of Science (46 page)

On the second of January 1700 Anthony van Leeuwenhoek [see p. 28], draper of Delft and self-taught Columbus of the littlest world, was writing to the Royal Society of London one of the many letters in which he described his voyages of discovery within a drop of water.

To William Dampier and other such rovers he left the exploration of the terrestrial globe. To another contemporary he left those equally adventurous voyages ‘through strange seas of thought, alone’ which took Newton across abysses of space to spheres much larger but not so little known as those to which Leeuwenhoek devoted his long life.

These worlds of his were not lifeless but teeming with life; and his discoveries, unlike those of Columbus, were discoveries in an absolute sense. He saw what no man, not merely no European man, had ever seen before. He had every right to be – he probably was – more amazed than Balboa.

The draper of Delft was already just short of seventy when he wrote:

There is no mistaking the fact that what had just swum into Leeuwenhoek’s ken was that very original and inventive organism, Volvox. Through hundreds of millions of years it had waited in countless places for man to become aware of its existence and, ultimately, to guess how important a step it had taken in the direction of both consciousness and that curiosity which was leading the Dutch draper to seek out in the ditches of Delft. The ‘little projecting particles’ are the peripheral cells which enclose the watery jelly in Volvox’s interior. The ‘5, 6, 7, nay some even 12, very little round globules, in structure like to the body itself are the vegetative ‘daughter cells’ produced by a sort of virgin birth between the sexual generations, much as in some of the higher plants ‘offsets’ as well as seeds are produced. Nor did Leeuwenhoek’s observation stop there:

In other words Leeuwenhoek saw both the liberation of the daughter colonies and also, though he did not realize its importance, something even more remarkable. He saw Volvox yielding to one of its two remarkable inventions – natural (or inevitable) Death. The other half of the strange story eluded him completely. He did not know that after a few generations have been vegetatively reproduced by the process he observed there comes a generation that will produce eggs which must be fertilized by sperm before they can develop.

Nearly three hundred years later and more than five thousand miles from Delft, I, in my late turn, have also been looking at Volvox still rolling along in his gracefully expert way. Like most of the free-living protozoa, he has established himself pretty well over the whole earth outside the regions of eternal ice and there is no use speculating how the cosmopolitan distribution was achieved or how he got to America. During the vast stretches of time which have been his, routes were open at one time or another from every part of the earth to every other part.

Historical plant geographers come almost to blows over the question how, for instance, the sweet potato got to the South Sea islands. But Volvox’s history goes back too far for even speculation or contention to reach. If only the fit survive and if the fitter they are the longer they survive, then Volvox must have demonstrated its superb fitness more conclusively than any higher animal ever has.

My equipment is as much superior to Leeuwenhoek’s as his originality, ingenuity, and persistence were superior to mine. Instead of a single blob of glass fixed in front of a tiny tube holding water and held up to sun or candlelight, I use the compound microscope, which was not brought to its present state until the second half of the nineteenth century. Light passes from a mirror through a complicated set of lenses designed to place it at exactly the right spot. An image is formed by another series of lenses, cunningly designed to correct one another’s faults and then form an image in a black tube, this image
again magnified by another set of lenses. I can confine Volvox to a hanging drop of water; I can light him from below, from the side, or even from the top. I can slow him down with sticky substances introduced into the drop; and I keep a supply of his species thriving in an artificial culture medium prepared for me by a biological supply house dealing in all sorts of improbable things. But though the beauty of Volvox must be even clearer to me than it was to Leeuwenhoek I have seen only what he saw and described in unmistakable terms.

Under a magnification of no more than a hunded diameters – called by microscopists ‘very low power’ – Volvox looks about the size of a marble and when motionless less like a plant-animal than like some sort of jeweler’s work intended, perhaps, as an earring. The surface of the crystal sphere is set with hundreds of tiny emeralds; its interior contains five or six larger emeralds disposed with careless
effectiveness
.

But Volvox is seldom motionless when alive and in good health. Bright as a jewel, intricate as a watch, and mobile as a butterfly, his revolutions bring one emerald after another into a position where they sparkle in the light. Though he is called the Roller [the English meaning of Latin,
Volvox
]
,
he actually
revolves
rather than
rolls,
because he seems to turn on an invisible axis, much as the planets do, and he moves forward with this axis pointing in the direction of his motion. His speed varies and he frequently changes direction but I once counted the seconds it took him to cross the field of the microscope and calculated that his speed, in proportion to his size, is comparable to that of a man moving at a fast trot. Volvox, however, suggests nothing so undignified as a trot. There is something majestic and, one might almost imagine, irresistible about his revolutions – again like those of a planet. One half expects to hear some music of the spheres.

Because the microscope has temporarily abolished the barrier of size which separates the universe of Volvox from my own, I enter temporarily into a dreamlike relationship with him, though he is unaware of my world and perhaps equally unaware of his own. Nevertheless there is an easy purposefulness in his movements and from what I have learned from the careful research of others I know that it is all much more complex and astonishing than I would ever have guessed or than Leeuwenhoek did guess.

When I lift my head from the microscope the dream vanishes. But it
is man and his consciousness which is really the fleeting dream. Volvox, or something very much like him, was leading his surprisingly complex life millions of years before man’s dream began and may well continue to do so for millions of years after the dream ends. Harder to realize is the fact that the enterprise and adventures of Volvox typify certain of the innovations and inventions which are casually summed up in the word ‘evolution’ and hence constituted some of the earliest and most essential steps toward making possible our dream.

Such acquaintance with Volvox as I have gained from my own casual observations is as superficial as what one gets from a moment’s examination of a flower or from peering with mild curiosity at some strange animal behind the bars of a zoo. Yet even so casual an examination will lead one to guess at some of the significant facts.

The predominant color of Volvox is green; the green looks like chlorophyl, and so it is. Moreover Volvox can be ‘cultured’ in a purely chemical solution. All of this suggests a plant rather than an animal, but biologists have decided that the classification is meaningless at this level. Both textbooks of zoology and textbooks of botany usually claim Volvox, and there are no hard feelings because zoologists and botanists agree that Volvox represents a stage of evolution at which plants have not diverged from animals. He is either the one or the other. Or, more properly, he is neither. He is not a plant or an animal; he is simply something which is alive.

Concerning another ambiguity the observer is likely to make an even better guess. The walls separating one cell from another are clearly marked out and each of the cells which lie upon the periphery of the sphere is exactly like the other peripheral cells. Every one of them looks like a complete one-celled creature, lashing its two flagella precisely as many such one-celled creatures do – although, as was mentioned a few pages back, it is easy to see that Volvox’s cells do not crack their whips independently because they are co-ordinated in such a way that the organism as a whole moves purposefully forward in a given direction as though the individual flagella were controlled by a central intelligence.

Yet the individual cells not only look like separate animals but are in fact morphologically all but indistinguishable from a certain very common specific free-living organism that occurs by the millions in stagnant rain water and is one of the usual causes why such water takes on a green color. Like this creature each of Volvox’s peripheral
cells has a nucleus, two flagella, and an ‘eye spot.’ Any observer might easily suppose that a number of such tiny creatures had recently got together and formed a ball; or, that the one-celled creatures were the result of the dissolution of Volvoxes. But if the one-celled creatures did form aggregates which then became cooperative, all that happened millions of years ago and for a very long time Volvox has been much more than a mere casual grouping. One of his peripheral cells cannot live without the others. He is at least as much one creature as many and he must live or die as a whole. He can no longer dissolve into the myriad of individuals of which, long ago, his ancestors were no doubt composed.

If you want to call him a multicelled animal you have to admit that the peripheral cells have retained a good deal of their original equipment for independent life. On the other hand if you want to call him a mere aggregation you have to concede that the individuals composing the colony have been co-ordinated, disciplined, and socialized to a degree no human dictator has yet even hoped to achieve in his ‘monolithic’ state. But in any event the guess that Volvox represents a stage in the development of the ‘higher’ multicellular animals and suggests how the transition was made is more
immediately
persuasive than many of the other guesses biology finds itself compelled to make.

Without comment I pass over the suggestion made sometimes with horror and sometimes with approval that our present-day society is in the process of taking a step analogous to that once taken by Volvox; that just as the one-celled animal cooperated until he was no longer an individual but part of a multicelled body, so perhaps the highest of the multicelled animals is now in the process of uniting to make a society in which he will count for as much and as little as an individual cell counts for in the human body.

Now comes the most powerful argument of all for calling Volvox a unified individual rather than even a tight social group and it has to do with three different sorts of cells sometimes found within his central jelly. The least remarkable of the groups of special cells are those composing the ‘daughter colonies’ which Leeuwenhoek saw and which in time will break out of the parent colony to start life on their own. About them there is nothing so very surprising, since ‘budding’ of one kind or another is not uncommon among microscopic
organisms. The other two groups of specialized cells are much more interesting because they seem to represent the first appearance of sexual differentiation.