Seeing Things

The doctrine of preformation, which dominated the theory of generation for most of the 18th century, asserted a single divine act of creation for all plant and animal life. The original ancestor of each species, it was believed, held within its body the entire series of its type, each future organism enclosed inside its parent, waiting to be stimulated into growth at the moment of conception. ‘Ovists’ held that the pre-existing germ resided in the female egg, while ‘spermists’ (Pinto-Correia’s neologism for ‘animalculists’) located it in the ‘spermatic animalcule’ discovered in 1677 by Leeuwenhoek; the dispute between them is the subject of Clara Pinto-Correia’s book.

Pinto-Correia is not a historian, but a professor of embryology, a novelist and a poet. She tells the story of how she came to write the book, with the help of the biologist Stephen Jay Gould, in her Introduction. Gould, for his part, does some contentious stage-setting in his Foreword, where, with the apparent aim of encouraging respect for the ‘important’, ‘influential’ and even ‘beautiful’ theory of preformation, he tells us that the ‘conceptual locks’ on our understanding of its place in the history of embryology are ‘better broken by the composition of this book than by any other document ever written in the history of science’.

Though her reliance on the earlier surveys of Francis Cole and Joseph Needham is evident, Pinto-Correia has read an impressive amount and surrounds her exposition with decorative flourishes of esoteric knowledge, concerning monsters, fecundation by the wind, Jurassic Park, masturbation, divine kingship, tarot cards, sperm-wars, the bell-curve, the Code of Manu, the meanings of ‘right’ and ‘left’, copper and iron, regeneration, the golem, Pythagoreanism, morphogenetic fields and more. She also manages to keep her eye on her main themes: the role of women in the history of biology and the 20th-century fate of preformation theory. One of the book’s achievements is its account of how the term ‘homunculus’ shifted from its original Paracelsian meaning – a sort of personal assistant created in a bottle from putrefied semen, for which Paracelsus promised to provide the secret recipe – and came, for moralising textbook writers, to denote the baby allegedly seen in the head of the spermatozoon by theory-driven observers with faulty microscopes.

Though it was associated with the introduction of the microscope in the mid-17th century, the theory of preformation was much older. The idea of invisible seeds containing pre-existent organisms was a classical notion, and Pinto-Correia describes its redeployment in the wake of the failure of mechanical philosophy to explain the origins and continuation of the species. Counter-Reformation ends were well served by this: if generation was merely the growth-by-accretion of particles of complete but very small organisms, the productive powers of nature were nullified. Arguing backwards, if only God and not nature could create new life, and if new life was constantly appearing, there manifestly was a God.

The most acute observers, including Aristotle, had always given preformation short shrift. ‘Epigenesis’ – the gradual emergence of embryonic organs and structures from an undifferentiated state of matter, under the controlling action of a local formative agent – could be directly inferred from macroscopic observation, and Fabricius and Harvey deduced it from their experiments with hen’s eggs. It might have been expected that the visual access to early stages of development afforded by the microscope would have confirmed these findings. This is not what happened, however. From 1668, van Horne, de Graaf and others began to find what they thought of as ‘eggs’ in the ovaries (formerly known as ‘female testicles’) of human females and other mammals. In 1669, Swammerdam discovered what he took to be the future butterfly, its legs and wings wrapped up and enfolded, in the pupa (the book contains a photograph of the ‘imaginal disks’ Swammerdam took for ‘wings’); then, in 1675, Leeuwenhoek discovered animalcules, smaller than any insects yet seen, first in infusions and later inside the bodies of animals, and shortly thereafter found living animalcules in semen. Meanwhile, Malpighi found ‘eggs’ in plants and faint delineations in the early embryo.

Neither the spermists (Leeuwenhoek, Andry and, for a time, Hartsoeker) nor the ovists (Malebranche, Haller, Senebier, Spallanzani, Bonnet), actually ‘saw’ through their microscopes the little human figures illustrated in textbooks. They did, however, claim to have visual evidence for the existence of small organisms pre- or immediately post-fertilisation. These sightings and the illustrations associated with them fall, with the notable exception of Leeuwenhoek’s three-day-old fully-formed ‘lamb’, into two distinct categories. The first comprises hesitant statements about what the observer thinks he might have glimpsed, or might be able to glimpse, were the viewing conditions better. The second comprises pictures and descriptions of little horses, dogs, chickens or babies, contributed by people wanting to get in on the act or trying to be funny. Other than this supposed evidence, preformation depended on the incoherence of the alternative. Its defenders conceded that preformed structures were transparent, covered with integuments, present only in rudimentary form, or otherwise difficult to visualise.

Pinto-Correia is right to say that the distinction between preformation and epigenesis was often blurred, and that people often resorted to compromise positions. By contrast, ovism and spermism were distinct alternatives. Spermism was compelling because the sperm, unlike the ‘egg’, was clearly an animal. It had a distinct ‘head’ and a ‘tail’ (like the early embryo); it was self-propelling, lived in flocks and even died. It went into the egg, Andry speculated, held the door shut behind it, and grew up. The role of the egg in spermism was obvious. Though huge, it could be seen as providing food, lots of it, and a soft, roomy habitat. The role of semen was harder for ovists to explain. They held that the spermatic animalcules were useless parasites, and believed the fertilising power lay in the ambient fluid. The ovist case was supported by analogy with the eggs of humans and other creatures, including plants, parthenogenesis, in which unfertilised eggs develop into organisms, and ectopic pregnancies. By 1721, however, the existence of eggs was again in doubt, and the old two-fluids theory, which posited equal contributions, was updated by Maupertuis, whose sensible experiments, calculations and deductions might, in a context in which being sensible counted for more, have seemed decisive.

Joseph Needham thought that spermism had lost the argument by 1747, when the ovist D’Aumont’s article in the Encyclopédie raised five compelling objections: that spermism implied God’s willingness to waste billions of tiny human lives for no apparent purpose; that animalcules of all species resembled each other; that they resembled other animalcules and microparasites; that they were never found in the uterus; that it was not clear how they reproduced their own kind. Pinto-Correia lays undue emphasis on the ‘wastage’ argument, associating it with masturbation taboos. Ovism held out for longer: F.J. Cole finds its last representative in the ‘belated but ardent ovist’ Pouchet in 1847. The cell-theory of the 1830s put a lower limit on the size of organisms, though Hartsoeker had abandoned preformation before his death in 1725, on finding that it implied a smallness ‘truly infinite and incomprehensible’. He calculated that a 1 followed by 60 zeros would be needed to represent the sum of dead, living and pre-existing rabbits. This incomprehensibility was subjective, however. The pious Haller, in his Elements of 1757, calculated that Eve would have had at least two hundred billion organisms encased within her, without including those to be born before the end of the world – this was fine with him. But by the mid-18th century, the age of the Earth and the origins of life were being backdated by hundreds of thousands of years from c.4000 BC, so that even the infinite powers of God appeared to be overtaxed. Meanwhile, epigenesis was sustained by the observation of embryos through adequate microscopes. The phenomenon of self-regeneration in starfish, salamanders and polyps came into prominence, and Newtonianism helped, by recertifying a non-mechanical force in nature: gravity. Finally, in 1790, Kant gave the idea of formative forces the philosophical stamp of approval in his usual authoritarian way.

The blurb of The Ovary of Eve assures us that the theory of generation was thought to bear on questions of nobility, paternity and inheritance, and tells us that ovists and spermists debated with one another at family dinner tables, and in palaces and cafés. Needham, quoting Cole, quoting J.M. Good, the translator of Lucretius (an example of literary emboîtement), states that in the fifty years before 1805, ‘every naturalist, and indeed every man who pretended to the smallest portion of medical science, was convinced that his children were no more related, in point of actual generation, to his own wife, than they were to his neighbours.’ If this extraordinary thesis were true, even for England alone, we should expect to find it widely echoed and questioned in medicine, in fiction and in legal judgments. But the topic of reception is not broached here, and we have little idea how books and articles in learned journals affected a wider public. We do learn from Pinto-Correia that both ovists and spermists believed that the perceptions and imagination of the mother were critical in determining her offspring’s appearance. For ovists, the mother’s thinking the right thoughts was needed to explain resemblance to the father; for spermists, a failure to resemble the father – or a likeness to someone, or something else in the case of ‘monsters’ – was highly suspicious and was invariably the mother’s fault, more precisely, her moral fault.

Pinto-Correia finds a powerful explanatory device in ‘the despised role occupied by women in the universal configuration of all natural philosophies’. It could be argued, however, that the 18th century was a happy respite between the misogyny of the fading Church and the misogyny of emerging academic institutions. Pinto-Correia mentions the hypothesis of sperm-warfare – the extermination or inactivation of the sperm of ‘foreign’ males by specially-evolved sperm. If, as has also been hypothesised, females have their own defence system, perhaps we can relax from the rigid code of male promiscuity and female coyness prescribed by sociobiologists to forestall degeneration of the race.

The charm of preformation is undeniable. People have always been delighted by miniaturisation, and the conceit of worlds within worlds stretches from Anaxagoras’ fantasy that every atom contains another civilisation to Leibniz’s monadology. Preformation came to seem a quaint and confining fancy, however, as admiration for copies and replicas, and ‘order descending into the smallest regions’, as Leibniz put it, gave way to the Romantic fascination with spontaneity and generation de novo. The origin of philosophical systems, Kant says, is like that of worms, from a generatio heteronyma.

Was preformation a beautiful theory, as Pinto-Correia and Gould claim? In its early manifestations it is more a theory of and about perfection; or else a way of talking and thinking about a perfection immune from chance and accident. The existence of monsters was not generally cited as evidence against its in the 18th century, but, while it prevailed, preformation was a charm against monsters. If epigenesis is true a thousand things can go wrong: men could have been born from apes, or might one day give birth to them. Geneticists continue to argue with developmental biologists over the notion that all is determined for us in advance – who is intelligent, who has intrinsic merit. Gould himself has been highly critical of this idea – his praise for the beauty of the theory of preformation constitutes an aesthetic, not a scientific, recommendation.