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Natural History
Feb, 1999

A Division of Worms.(Jean Baptiste Lamarck's contributions to evolutionary theory)(Part One)
Author/s: Stephen Jay Gould

The use and disuse of Lamarck

PART ONE: The Spirit of Lamarck's System

I. The Making and Breaking of a Reputation On the twenty-first day of the auspiciously named month of Floreal (flowering), in the spring of the year 8 on the French revolutionary calendar (1800 to the rest of the Western world), the former Chevalier (knight) but now Citoyen (citizen) Lamarck delivered the opening lecture for his annual course on zoology at the Museum d'Histoire Naturelle in Paris--and changed the science of biology forever by presenting the first public account of his theory of evolution. Lamarck then published this short discourse in 1801, as the first part of his treatise on invertebrate animals, Systeme des animaux sans vertebres (System of invertebrate animals).

Jean-Baptiste Lamarck (1744-1829) had enjoyed a distinguished career in botany when, just short of his fiftieth birthday, he became a professor of "insects, worms, and microscopic animals" at the Museum d'Histoire Naturelle, newly constituted by the Revolutionary government in 1793. Lamarck would later coin the term invertebrate for his assigned organisms. (In 1802 he also introduced the word biology for the entire discipline.) But his original title followed Linnaeus's designation of all spineless animals as either insects or worms, a Procrustean scheme that Lamarck would soon alter. Lamarck had been an avid shell collector and student of mollusks (then classified within Linnaeus's large and heterogeneous category of Vermes, or worms)--qualifications deemed sufficient for his shift from botany.

Lamarck fully repaid the confidence invested in his general biological abilities by publishing distinguished works in the taxonomy of invertebrates throughout the remainder of his career, culminating in the seven volumes of his comprehensive Histoire naturelle des animaux sans vertebres (Natural history of invertebrate animals), published between 1815 and 1822. At the same time, he constantly refined and expanded his evolutionary views, extending his introductory discourse of 1800 into a full book in 1802 (Recherches sur l'organisation des corps vivants, or "Research on the organization of living beings"); then into his magnum opus and most famous work in 1809, the two-volume Philosophie zoologique (Zoological philosophy); and finally into a statement for the long opening section, published in 1815, of his great treatise on invertebrates.

The outlines of such a career might seem to imply continuing growth of prestige, from an initial flowering to the full bloom of celebrated seniority. But Lamarck's reputation suffered a spectacular collapse, even during his own lifetime, and he died lonely, blind, and impoverished. The complex reasons for his reverses include the usual panoply of changing fashions, powerful enemies, and self-inflicted wounds based on flaws of character (in his case, primarily an overweening self-assurance that could not face, or even recognize, the weaknesses in some of his own arguments or the skills of his adversaries). Most prominently, his favored style of science--the construction of grand and comprehensive theories, following an approach that the French call l'esprit de systeme (the spirit of system building), and not always well supported by testable data--became notoriously unpopular after the rise of a hard-nosed, empiricist ethos in early nineteenth-century geology and natural history.

In one of the great injustices of our conventional history, Lamarck's disfavor has persisted to our times, and most people still know him only as the foil to Charles Darwin's greatness--as the man who proposed a silly theory about giraffes stretching their necks to reach high leaves and then passing the fruits of their efforts to their offspring by "inheritance of acquired characters," otherwise known as the hypothesis of use and disuse, in contrast with Darwin's proper theory of natural selection and survival of the fittest.

Indeed, the usually genial Darwin had few kind words for his French predecessor. In letters to his friends, Darwin dismissed Lamarck as an idle speculator with a nonsensical theory. In 1844 he wrote to the botanist Joseph D. Hooker on the dearth of evolutionary thinking (before his own ideas about natural selection): "With respect to books on the subject, I do not know of any systematical ones except Lamarck's, which is veritable rubbish." To his guru, the geologist Charles Lyell (who had accurately described Lamarck's system for English readers in the second volume of his Principles of Geology, published in 1832), Darwin wrote in 1859, just after publishing the Origin of Species: "You often allude to Lamarck's work; I do not know what you think about it, but it appeared to me extremely poor; I got not a fact or idea from it."

But these later and private statements did Lamarck no practical ill. Far more harmfully, and virtually setting an "official" judgment from that time forward, his eminent colleague Georges Cuvier (the brilliant biologist, savvy statesman, distinguished man of letters, and Lamarck's younger and anti-evolutionary fellow professor at the museum) used his established role as writer of eloges (obituary notices) for deceased colleagues to compose a cruel masterpiece in the genre of "damning with faint praise"--a document that fixed and destroyed Lamarck's reputation. Cuvier began with cloying praise and then described his need to criticize as a sad necessity:

   In sketching the life of one of our most celebrated naturalists, we have
   conceived it to be our duty, while bestowing the commendation they deserve
   on the great and useful works which science owes to him, likewise to give
   prominence to such of his productions in which too great indulgence of a
   lively imagination had led to results of a more questionable kind, and to
   indicate, as far as we can, the cause or, if it may be so expressed, the
   genealogy of his deviations.

Cuvier then proceeded to downplay Lamarck's considerable contributions to anatomy and taxonomy and to excoriate his senior colleague for fatuous speculation about the comprehensive nature of reality. Cuvier especially ridiculed his subject by contrasting his caricature of Lamarck's ideas with the sober approach of proper empiricism:

   These [evolutionary] principles once admitted, it will easily be perceived
   that nothing is wanting but time and circumstances to enable a monad or a
   polypus gradually and indifferently to transform themselves into a frog, a
   stork, or an elephant.... A system established on such foundations may
   amuse the imagination of a poet; a metaphysician may derive from it an
   entirely new series of systems; but it cannot for a moment bear the
   examination of anyone who has dissected a hand ... or even a father.

Cuvier's eloge reeks of exaggeration and unjust ridicule, especially toward a colleague ineluctably denied the right of response--the reason, after all, for our venerable motto De mortuis nil nisi bonum (Say only good of the dead). But Cuvier did base his disdain on a legitimate substrate, for Lamarck's writing certainly shows a tendency to grandiosity in its comprehensive pronouncements, combined with frequent refusal to honor, or even to consider, alternative views with strong empirical support.

L'esprit de systeme, the propensity for constructing complete and overarching explanations based on general and exceptionless principles, may apply to some corners of reality but works especially poorly in the maximally complex world of natural history. Lamarck did feel drawn to this style of system building, and he showed no eagerness to acknowledge exceptions or to change his guiding precepts. But the rigid and dogmatic Lamarck of Cuvier's caricature can be regarded only as a great injustice, for the man himself did maintain appropriate flexibility before nature's richness and did eventually alter the central premises of his theory when his own data on the anatomy of invertebrate animals could no longer sustain his original view.

This fundamental change--from a linear to a branching system of classification for the basic groups, or phyla, of animals--has been well documented in standard sources of modern scholarship about Lamarck (principally in Richard W. Burkhardt Jr.'s The Spirit of System: Lamarck and Evolutionary Biology, Harvard University Press, 1977; and Pietro Corsi's The Age of Lamarck: Evolutionary Theories in France 1790-1830, University of California Press, 1988). But the story of Lamarck's intellectual journey remains incomplete, for both the first explicit statement and the final conclusion have been missing from the record--the beginning because Lamarck noted his first insight as a handwritten insertion, heretofore unpublished, in his own copy of his first printed statement about evolution (the Floreal address of 1800, recycled as the preface to his 1801 book on invertebrate anatomy); and the ending because his final book of 1820, Systeme analytique des connaissances positives de l'homme (Analytic system of positive knowledge of man), has been viewed only as an obscure swan song about psychology--a rare book even more rarely consulted, despite a fascinating section containing a crucial and novel wrinkle on Lamarck's continually changing views about the classification of animals. Stories deprived of both beginnings and endings cannot satisfy our urges for fullness or completion--and I am grateful for this opportunity to supply these terminal anchors in this two-part essay.

II. Lamarck's Theory and Our Misreadings

Lamarck's original evolutionary system--the logical, pure, and exceptionless scheme that nature's intransigent complexity later forced him to abandon--featured a division of causes into two independent sets, responsible for progress and diversity, respectively. (Scholars generally refer to this model as the "two factor theory.") On the one hand, the "force that tends incessantly to complicate organization" (la force qui tend sans cesse a composer l'organisation) leads evolution inexorably upward, beginning with the spontaneous generation of infusorians (single-celled animals) from chemical precursors, and moving on toward human intelligence.

But Lamarck recognized, on the other hand, that the riotous diversify or living organisms could not be ordered into a neat and simple series of linear advances--for what could come directly before or after such marvels of adaptation as long-necked giraffes, moles without eyes, flatfishes with both eyes on one side of the body, snakes with forked tongues, or birds with webbed feet? Lamarck therefore advocated linearity only for the "principal masses," or major anatomical designs of life's basic phyla. Thus, he envisioned a linear sequence--mounting in perfect, progressive regularity--from infusorian to jellyfish to worm to insect to mollusk to vertebrate. He then depicted the special adaptations of particular lineages as lateral deviations from this main sequence.

These special adaptations originate by the second set of causes, labeled by Lamarck as "the influence of circumstances" (l'influence des circonstances). Ironically, this second (and subsidiary) set has descended through history to become the Lamarckism of modern textbooks and anti-Darwinian iconoclasts, while the more important first set of linearizing forces has been forgotten. This second set--based on change of habits as a spur to adaptation in new environmental circumstances--invokes the familiar (and false) doctrines now called Lamarckism: the inheritance of acquired characters and the principle of use and disuse.

Lamarck invented nothing original in citing these principles of inheritance, for both doctrines represented the folk wisdom of his time (despite their later disproof in the new world of Darwin and Gregor Mendel). Thus, the giraffe stretches its neck throughout life to reach higher leaves on acacia trees, and the shorebird extends its legs to remain above the rising waters. This sustained effort leads to longer necks or legs--and these rewards of hard work then descend to offspring in the form of altered heredity (the inheritance of acquired characters, either enhanced by use, as in these cases, or lost by disuse, as in eyeless moles or blind fishes living in perpetually dark caves).

As another irony and injustice (though abetted, in part, by Lamarck's own unclear statements), the ridicule surrounding Lamarck's theory, ever since Cuvier's eloge and Darwin's dismissal, has always centered on the charge that his views represent a sad throwback to the mystical vitalism of bad old times, before modern science enshrined testable mechanical causes as the proper source of explanation. What genuine understanding, critics charge, can possibly arise from claims about vague and unknowable powers inherent in life itself, either propelling organisms upward by an intrinsic complexifying force (recalling Moliere's famous mock of vitalistic medicine, exemplified in the claim that morphine induces sleep quia est in eo virtus dormativa, "because it contains a dormitive virtue"), or sideward by some ineffable "willing" to build an adaptive branch by sheer organic effort or desire?

In a famous letter to Hooker, his closest confidant, Darwin first admitted his evolutionary beliefs in 1844 by contrasting his own mechanistic account with a caricature of Lamarck's theory: "I am almost convinced ... that species are not (it is like confessing a murder) immutable. Heaven forfend me from Lamarck nonsense of a `tendency to progression,' `adaptations from the slow willing of animals,' etc.! But the conclusions I am led to are not widely different from his; though the means of change are wholly so." And Cuvier, in a public forum, ridiculed Lamarck's second set of adaptive forces in the same tone: "Wants and desires, produced by circumstances, will lead to other efforts, which will produce other organs. ... It is the desire and the attempt to swim that produces membranes in the feet of aquatic birds. Wading in the water ... has lengthened the legs of such as frequent the sides of rivers."

Lamarck hurt his own cause by careless and easily misinterpreted statements. His talk about an "inner urge" (sentiment interieur) to propel the upward force, or about organisms obeying "felt needs" (besoins, in his terminology) to induce sideward branches of adaptation, led to suspicions about mysterious and unprovable vitalistic forces. But, in fact, Lamarck remained a dedicated and vociferous materialist all his life--a credo that surely represents the most invariable and insistent claim in all his writings. He constantly sought to devise mechanical explanations, based on the physics and chemistry of matter in motion, to propel both sets of forces--linear and lateral. I do not claim that his efforts were crowned with conspicuous success--particularly in his speculative efforts to explain the linear sequence of animal phyla by positing an ever more vigorous and ramifying flow of fluids that carved out spaces for organs, and channels for blood, in progressively more complex bodies. But one cannot deny his consistent conviction. "La vie ... n'est autre chose qu'un phenomene physique (Life is nothing but a physical phenomenon)," he wrote in his last book of 1820. In a famous article, written to rehabilitate Lamarck on the occasion of the centennial celebrations for Darwin's Origin of Species in 1959, the eminent historian of science C. C. Gillispie wrote: "Life is a purely physical phenomenon in Lamarck, and it is only because science has (quite rightly) left behind his conception of the physical that he has been systematically misunderstood and assimilated to a theistic or vitalistic tradition which in fact he held in abhorrence."

Lamarck depicted his two sets of evolutionary forces as clearly distinct and destined to serve contrasting ends. The beauty of his theory--the embodiment of his esprit de systeme--lies in this clean contrast of both geometry and mechanism. The first set works upward to build progress in a strictly linear series of major anatomical designs (phyla) by recruiting mechanisms inherent in the structure and motion of living matter. The second set works sideward to extract branches made of individual lineages (species and genera) that respond to the influence of external circumstances by precise adaptations to particular environments. (These side branches may be visualized as projecting at right angles, perpendicular to the main trunk of progress. Vectors at right angles are termed orthogonal, and are mathematically independent, or uncorrelated).

Lamarck made this contrast explicit by stating that animals would form only a single line of progress if the pull of environmental adaptation did not interrupt, stymie, and divert the upward flow in particular circumstances:

   If the factor which works incessantly to complicate organization were the
   only one which had any influence on the shape and organs of animals, the
   growing complexity of organization would everywhere be very regular. But it
   is not; nature is forced to submit her works to the influence of their
   environment.... This is the special factor which occasionally produces ...
   the often curious deviations that may be observed in the progression.
   (Philosophie Zoologique, 1809)

Thus, the complex order of life arises from the interplay of two forces in conflict, with progress driving lineages up the ladder and adaptation forcing them aside into channels set by the peculiarities of local environments:

   The state in which we find any animal is, on the one hand, the result of
   the increasing complexity of organization tending to form a regular
   gradation; and, on the other hand, of the influence of a multitude of very
   various conditions ever tending to destroy the regularity in the gradation
   of the increasing complexity of organization. (Philosophie zoologique,

Finally, in all his major evolutionary works, culminating in his multivolume treatise on invertebrate anatomy, Lamarck honored the first set of linear forces as primary and identified the second set as superposed and contrary--as in this famous statement, where he brands the lateral pull of adaptation as foreign, accidental, interfering, and anomalous:

   The plan followed by nature in producing animals clearly comprises a
   predominant prime cause. This endows animal life with the power to make
   organization gradually more complex.... Occasionally a foreign, accidental,
   and therefore variable cause has interfered with the execution of the plan,
   without, however, destroying it. This has created gaps in the series, in
   the form either of terminal branches that depart from the series in several
   points and alter its simplicity, or of anomalies observable in specific
   features of various organisms. (Histoire naturelle des animaux sans
   vertebres, 1815)

III. The Values of Changing Theories

Charles Darwin began the closing paragraph of his Origin of Species with a wonderful line that has served as the general title for these essays since I began the series in 1974: "There is grandeur in this view of life...." No thinking or feeling person can deny either nature's grandeur or the depth and dignity of our discovery that a history of evolution binds all living creatures together. But in our world of diverse passions and psychologies, primary definitions (and visceral feelings) about grandeur differ widely among students of natural history. Darwin emphasized the bounteous diversity itself, in all its buzzing and blooming variety--for the finale of his closing paragraph contrasts the "dullness" of repetitive planetary cycling with the endless expansion and novelty of evolution's good work: "Whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved."

But I suspect that Lamarck, following his own upbringing in the rigorous traditions of French rationalism during the Enlightenment, construed the definition of grandeur quite differently. As a devotee of l'esprit de systeme, Lamarck surely viewed the capacity of the human mind (his own in this case, for he was not a modest man) to apprehend the true and complete system of nature's rational order as the most remarkable feature of all. Thus, the logical clarity of the two-factor theory--with the primary cause establishing a linear march of rational progress and the opposed and subsidiary cause generating a more chaotic forest of adaptive diversity--must have struck Lamarck as the defining component both of nature's grandeur and of the power of evolution.

Our understanding of nature must always reflect a subtle interaction between messages from genuine phenomena truly out there in the real world, and the necessary filtering of such data through all the foibles and ordering devices internal to the human mind and its evolved modes of action. We cannot comprehend nature's complexity--particularly for such comprehensive subjects as evolution and the taxonomic structure of nature's diversity--unless we impose our mental theories of order upon the overt chaos that greets our senses. The different styles followed by scientists to balance and reconcile these two interacting (but partly contradictory) sources of order virtually define the rich variety of fruitful approaches pursued by a profession too often, and falsely, caricatured as a monolithic enterprise committed to a set of fixed procedures called the scientific method. Dangers and opportunities attend an overemphasis on either side. Rigid systematizers often misconstrue natural patterns by forcing their observations into rigidly preconceived structures of explanation. But colleagues of the opposite bent, who try to approach nature on her own terms, without preferred hypotheses to test, risk being either overwhelmed by a deluge of confusing information or falling prey to biases that become all the more controlling by their unconscious (and therefore unrecognized) status.

In this spectrum of useful approaches, Lamarck surely falls into the domain of scientists who place the logical beauty of a fully coherent theory above the messiness of nature's inevitable nuances and exceptions. In this context, I am all the more intrigued by Lamarck's later intellectual journey, so clearly contrary to his inclinations and inspired (in large part) by his inability to encompass new discoveries about the anatomy of invertebrates within the rigid confines of his beautiful system.

Nothing in the history of science can be more interesting or instructive than the intellectual drama of such a slow transformation in a fundamental view of life--from an initial recognition of trouble, to attempts at accommodation within a preferred system, then to varying degrees of openness toward substantial change, and sometimes even to full conversion. I particularly like to contemplate the contributions of external and internal factors to such a change: new data mounting a challenge from the outside, coordinated with an internal willingness to follow the logic of an old system to its points of failure and then to construct a revised theory imposing a different kind of consistency upon an altered world (with minimal changes if you remain in love with your previous certainties and tend to follow conservative intellectual strategies, or with potentially revolutionary impact if your temperament leads to iconoclasm and adventure). Reward and risk go hand in hand, for the great majority of thoroughly radical revisions must fail, even though the sweetest fruits await the few victors in this chanciest and most difficult of all mental battles.

When we can enjoy the privilege of watching a truly great intellect struggling with the most important of all biological concepts at a particularly interesting time in the history of science, then all factors coincide to generate a wonderful story offering unusual insight into the workings of science as well. When we can also experience the good fortune of locating a previously missing piece of history--in this case, the first record of a revision that would eventually alter the core of a central theory, although Lamarck, at this inception, surely had no inkling of how vigorously such a small seed could grow--we then gain the further blessing of an intriguing particular (the substrate of all good gossip) grafted onto an important generality. The prospect of being an unknown witness--the "fly on the wall" of a common metaphor--has always excited our fancy. And the opportunity to intrude upon a previously undocumented beginning--to be "present at the creation," in another common description--evokes an extra measure of charm. In this case, we begin with something almost inexpressibly humble--the classification of worms--and end with both a new geometry for animal life and a revised vision of evolution itself.

IV. Lamarck Emends His First Evolutionary Treatise

Once upon a time, in a faraway world before the electronic revolution, and even before the invention of typewriters, authors submitted literal manuscripts (from the Latin for "written by hand") to their publishers. When writers revised a book for a second edition, they often worked from a specially prepared "interleaved copy" containing a blank sheet after each printed page. Corrections and additions could then be written on the blanks, enabling publishers to set a new edition from a coherent, bound document rather than from a confusing mess of loose or pasted insertions. Lamarck owned an interleaved copy of his first evolutionary treatise--the Systeme des animaux sans vertebres of 1801. Although he never published a second edition, he did make comments on the blank pages--and he incorporated some of these statements into later works, particularly the Philosophie zoologique of 1809. This copy, which might have tempted me to a Faustian form of collusion with Mephistopheles if the opportunity had been offered, recently sold at auction for more money than even a tolerably solvent professor could ever dream of having at his disposal. But I was able to play the intellectual's usual role of voyeur during the few days of previewing before the sale, and I did recognize, in a crucial note in Lamarck's hand, a significance that had eluded previous observers. The eventual buyer (still unknown to me) expressed gratitude for the enhanced importance of his purchase, and he kindly offered (through the bookseller who had acted as his agent)to lend me the volume for a few days and allow me to publish the key note in this forum. I floated on cloud nine and happily rooted like a pig in ... during those lovely days when I could hold and study my profession's closest approach to a holy grail.

Lamarck did not make copious additions on the interleaved copy, but several of his notes offer intriguing insights, while their general tenor teaches us something important about the relative weighting of his concerns. The first 48 pages of the printed book contain the Floreal address, Lamarck's initial statement of his evolutionary theory; the final 350 pages present a systematic classification of invertebrates, including a discussion of principles and a list and description of all recognized genera, treated phylum by phylum. Of Lamarck's thirty-seven handwritten additions on the blank pages, twenty-nine offer only a word or two and represent the ordinary activity of correcting small errors, inserting new information, or editing language. Lamarck makes fifteen comments about anatomy, mostly in his chapter on the genera of mollusks, the group he knew best. A further nine comments treat taxonomic issues of naming (adding a layman's moniker to the formal Latin designation, changing the name or affiliation of a genus); two add bibliographic data; and the final three edit some awkward language. Taken as an ensemble, I regard these comments as informative in correcting a false impression that Lamarck, by this time of seniority in his career, cared only for general theory and not for empirical detail. Clearly Lamarck continued to cherish the minutiae of raw information and to keep up with developing knowledge--the primary signs of an active scientific life.

Of the eight longer comments, four appear as additions to the Floreal address. They provide instructive insight into Lamarck's character and concerns by fulfilling the conservative function of making more explicit--and elaborating by hypothetical examples--the central feature of his original evolutionary theory: the sharp distinction between causes of upward progress and sideward adaptation to local circumstances. In the two comments that attracted the most attention from potential buyers, Lamarck added examples of adaptation to local environments by inheritance of acquired characters: first, flatfishes living in shallow water that flatten their body to swim on their side and then move both eyes to the upper surface of their head; and second, snakes that move their eyes toward the top of their head since they live so close to the ground and must therefore perceive a world of danger above them, but that then need to develop a long and sensitive forked tongue to perceive the trouble in front that the eyes can no longer see. With these examples, Lamarck generalized his second set of forces by extending his stories to a variety of organisms; the Floreal address had confined itself to illustrations drawn from the habits and anatomy of birds. (The purely speculative character of these examples also helps us to understand why more sober empiricists, like Darwin and Cuvier, felt so uncomfortable with Lamarck's supposed data for evolution.) In any case, Lamarck published both examples almost verbatim in his Philosophie zoologique of 1809. A third comment then strengthens the other, and primary, linear force by arguing that the newly discovered platypus of Australia could link the penultimate group (birds) to the highest group (mammals). The fourth comment tries to explain the mechanisms of use and disuse by the differential flow of fluids through bodies.

The other set of four longer comments adorns the second part of the book, on taxonomic ordering of invertebrate animals. One insertion suggests that a small and enigmatic egg-shaped fossil should be classified within the phylum of corals and jellyfishes. A second statement, of particular interest to me, revises Lamarck's description of the clam genus Trigonia. This distinctive mollusk had long been known as a prominent fossil in Mesozoic rocks, but no Tertiary fossils or living specimens had ever been found, and naturalists therefore posited an extinction for Trigonia in the great Cretaceous mass dying that also wiped out the dinosaurs. But two French naturalists then found a living species of Trigonia in Australian waters in 1802, and Lamarck himself published the first description of this triumphant rediscovery in 1803. (As an undergraduate, I did my first technical research--and also wrote my first paper in the history of science--under the direction of Norman D. Newell at the American Museum of Natural History. He gave me a half-dozen, still preciously rare, specimens of modern Australian trigonians. When I gulped and admitted that I had no experience with dissection and feared butchering such a valuable bounty, he said to me, in his laconic manner--so inspirational for self-motivated students but so terrifying for the insecure--"Go down to the Fulton Fish Market and buy a bunch of quahogs. Practice on them first." I was far more terrified than inspired, but all's well that ends well.)

The final two comments provide the greatest visceral pleasure of all, because Lamarck added drawings to his words (reproduced here with the kind permission of the book's new owner). The first sketch affirms Lamarck's continuing commitment to detail and to following and recording new discoveries. A small, white, delicate coiled shell of a cephalopod mollusk (the group including squid and octopuses) frequently washes up on beaches throughout the world. On the basis of this structure, Lamarck had proposed the genus Spirula in 1799, but the animal that makes the shell had never been found. As a particular mystery, no one knew whether the animal lived inside the shell (as in a modern chambered nautilus) or grew the shell within its body (as in the cuttlebone of a modern squid). The delicacy of the structure suggested a protected internal status, but the issue remained open. Soon after Lamarck's book appeared, naturalists discovered the animal of Spirula and affirmed an internal shell--a happy resolution that inspired Lamarck to a rare episode of artistic activity.

The last--and, as I here suggest, by far the most important--comment appears on the blank sheet following page 330, which contains descriptions of two remarkably different genera of worms--the medicinal leech Hirudo and the pond worm Planaria, known to nearly anyone who ever took a basic laboratory course in biology. Here Lamarck draws a simple sketch of the circulatory system of an annelid worm and then writes the following portentous words:

   observation sur, [l'org.sup.on] des vers. dans les vers anneles et qui ont
   des organs externes, le sang est rouge et circule dans des vaisseaux
   arteriels et veineux, leur organisation les place avant les insectes, les
   vers intestins doivent seuls se trouver apres les insects, ils n'ont qu'un
   fluide blanc, libre, non contenu dans des vaisseaux. Cuvier. extrait d'un
   mem. lu a l'institut le 11 nivose an 10.

   (Observation on the organization of worms. In annelid worms, which have
   external organs, the blood is red and circulates in arterial and venous
   vessels. Their organization places them before the insects. Only the
   internal worms come after the insects. They have only a white fluid, free,
   and not contained in vessels. Cuvier. Extract from a memoir read at the
   Institute on the 11th day of the month of Nivose year 10 of the Republic.)

Clearly Lamarck now recognizes a vital distinction between two groups that had once been lumped together into the general category of worms. He regards one group--the annelids, including earthworms, leeches, and the marine polychaetes--as highly advanced, even more so than insects. (Lamarck usually presented his scale of animal life from the top down, starting with humans and ending with infusorians, rather than following the later convention of working upward. Thus, he states that annelids come before insects because they are more advanced--that is, closer to the mammalian top.) But another group, the internal worms(*) (mostly parasites living within the bodies of other animals), rank far lower on the scale--even after (that is, anatomically simpler than) insects. These two distinct groups, previously conflated, must now be widely separated in the taxonomic ordering of life. Ironically, Lamarck acknowledges his colleague Cuvier (who would later turn against him and virtually destroy his reputation) as the source for a key item of information that changed his mind--Cuvier's report (presented at a meeting during the winter of 1801-1802, soon after the publication of Lamarck's book) that annelids possessed a complicated circulatory system, with red blood running in arteries and veins, whereas internal worms grew no discrete blood vessels and moved only a white fluid through their body cavity.

Obviously Lamarck viewed this new information as especially important, for no other anatomical note receives nearly such prominence in his additions, while only one other observation (a simple new bit of information, without much theoretical meaning) merits a drawing. But why did Lamarck view this division of worms as so important? And how could such an apparently dull and technical decision about naming act as a pivot and initiator for a new view of life?

(At this point, dear reader, limitations of space trump the prospect of immediate gratification. And so, with great reluctance--and with a request that you direct your complaints to the management, as no author in history has ever objected to more space--I must impose the "Perils of Pearl Pureheart" scenario upon you and beg your indulgence until the next thrilling episode, when Lamarck's worm will, in Emerson's words, "mount through all the spires of form" to ramify its author's view of life. Have a good month hanging from yonder mental cliff! I shall return.)

(*) The standard English literature on this subject always translates Lamarck's phrase incorrectly as "intestinal worms." These parasites dwell in several organs and other locations in vertebrate (and other) bodies, not only in the intestines. In French, the word intestin conveys the more general meaning of "internal" or "inside."

Stephen Jay Gould teaches biology, geology, and the history of science at Harvard University. He is also the Frederick P. Rose Honorary Curator in Invertebrates at the American Museum of Natural History.

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