I am grateful to Manhattan Community College, CUNY, for the Faculty Publication Grant that allowed me to complete this project. Note: in the following pages NS refers to Robert C. Stauffer’s edition of Darwin’s 1856-1858 writings on natural selection; see bibliography. Ed. Robert C. Stauffer. 1975

In the drafts of what became The Origin of Species that Charles Darwin wrote between 1842 and 1844, he employed two kinds of hypothetical explanations of how the principle of natural selection worked. The development of his ideas of natural selection can therefore be traced through the following texts: (1) the Notebooks of 1838-1839; (2) the 1842 and 1844 early drafts, published posthumously in 1909; (3) an abstract of the principle sent to the botanist, Asa Gray (1808-1888), on 5 September 1857 ("Abstract of a Letter," 50-53); (4) drafts of a "Natural Selection" chapter, begun in March 1857 and completed on 31 March 1858 (NS, 218-74); (5) the 1859 Origin of Species and later editions; and, finally, (6) The Variation of Animals and Plants under Domestication .

Charles Darwin. Maull & Polyblank Circa 1855. Albumen print, arched top, 7 7/8 in. x 5 3/4 in. (200 mm x 146 mm). Click on image to enlarge it. National Portrait Gallery NPG P106(7), Purchased, 1978. Click on image to enlarge it.

According to Darwin, natural selection operated through a network of interactions and generational effects involving plants and animals in the struggle for survival. To convey how the process might unfold, he wrote two kinds of explanatory narratives, which I review below. In the first or empirical narrative, Darwin presented the hypothetical events of natural selection strictly in terms of observable phenomena upon which he based his principle. This kind of narrative portrays the interactivity of organisms under certain environmental conditions. Darwin examines a series of possible outcomes, demonstrating how, over generations, aggregated effects can lead to adaptations that increase the survival of some species and the extinction of others (Origin (1859), 80-81; Cain 468-86).

In the second or what I call the demiurgic narrative, Darwin employed a subordinate deity to determine biological outcomes. In both the empirical and demiurgic narratives, he describes a network of interconnected events, the adaptation of species to the conditions of the biome, and the extinction of the unfit ("Demiurge," OED, I: 683; Blunt; Limoges 23-4; O'Brien 2-4); however, from 1842 to 1868, his inclusion of a Demiurge as a creative source and agent of biotic activity directly contradicted the standard definition of natural selection as it developed through the abovementioned texts. According to the 1859 definition, in a common habitat Darwin's principle modifies species through the interactions of plants and animals and through hereditary factors over the course of generations. Only by 1868 did Darwin realize that a semi-divine figure, who served as a teleological agency, contradicted the fundamental premise of natural selection — that organisms survive or perish through a nonintelligent process.

Neither Darwin's contemporary critics nor his supporters could understand why he used such a subordinate deity in narratives explaining a scientific theory. Victorian commentators therefore interpreted the Demiurge in three ways —  as a puzzling anachronism; as a veiled critique of orthodox natural theology; or, as Charles Lyell (1797-1875) observed in a 15 June 1860 letter to Darwin, as a deification of nature (Wollaston 133; Lyell DCP-LETT-2832A; Müller 2: 617; DuBois 7). Modern commentators have offered other explanations (see below).

The threefold object of this essay is to present the rhetorical paradox of the natural selection texts; to suggest, on the basis of Darwin's reluctance to abandon the demiurgic narrative, that he may not have appreciated the degree to which it threatened his argument; and, consonant with the place-holder, exogeneity, and algorithmic perspectives, to demonstrate that, by 1868, he abandoned the Demiurge once he had formulated the provisional theory of pangenesis, a flawed attempt to explain the hereditary mechanism of Natural Selection.

The Empirical Explanatory Narrative

Two passages below demonstrate both Darwin's rigorous evaluation of material data and his ability to explain that natural selection acts in the biome by means of a network of reciprocal relations. His posthumously published 1844 notes contain the empirical narrative in which the stages of natural selection appear as observable phenomena: a canine predator (fox or dog) that subsists "chiefly on rabbits, but sometimes on hares" (1844, 91). When a rabbit population slowly decreases, either because of hereditary, environmental factors, or both, a fox or dog must find an alternative food source or starve. At the same time, the hare population, a secondary source of food, begins to increase withouts predator fast enough to catch them and thereby control their reproductive numbers. If an emergent subtype of the canine predators develops inheritable traits favorable to catching hares, this provides them an abundant food source. Light and agile, equipped with long limbs and acute eyesight, the canine subtype has a slight advantage over their slower, less-visually acute forebears. The slower forebears, without rabbits and unable to capture hares, therefore decline in number, even to the point of extinction. The long-range outcome of this natural course of events would be an increase in the population of fast, well-nourished canine hunters; in turn, this would produce high numbers of offspring tending "to inherit these slight peculiarities"; and the agile canines would be poised to supplant their slower forebears (92).

Although Darwin did not know how heredity worked, his explanatory narrative still outlines the interconnected effects that arise if the physical characteristics and environmental conditions in an ecosystem change even slightly. He demonstrates that the loss of a primary food source can result in the extinction of maladapted predators and in the emergence — and dominance — of the more versatile hunters.

An 1857 empirical narrative exemplifies Darwin's idea of how organisms can beneficially interrelate with each other. The vignette below, from the 31 March 1857 chapter, "On Natural Selection," concerns the physiology of nectar-producing flowers, such as those belonging to the Genus Leguminosae (NS, 221-22). At the base of the flowery stalks, two lateral outgrowths called stipules excrete a sweet juice that eliminates injurious substances from the sap (Dutta 23). Insects feeding on the excretion would likely come in contact with the inner bases of the petals and be dusted with pollen. When the insects carry pollen to stigmas of another flower, they facilitate a cross between the two conspecific plants. Darwin had every reason to believe that such a crossing would produce "more vigorous seedlings," in the long run improving the species' chance of survival, because some of them would inherit the nectar-excreting trait. Individual flowers of the second generation, which excrete more nectar than had the parental stock, attract more insects; the more insects, the greater the dispersal of pollen with that hereditary trait; and the more progeny would inherit it.

In this explanatory narrative, Darwin used the example of the development of a physiological variation that increased nectar production. Stamens and pistils, which randomly had become altered to accommodate particular insects, had acquired a secondary, adaptative trait. An alternative outcome could result if insects were to ingest pollen instead of nectar. Although a pollen-feeder would consume most of the male microspores, pollen obtained by contact could also be an ancillary means of cross-fertilization that became a possible source of variation. Like the nectar-producing plant, those producing large quantities of pollen and having anthers larger than those of their forebears, would have been naturally selected, their survival advantage being the direct result of cross-pollination (NS, 221). Darwin also envisaged during this interaction a physical benefit accruing to certain insects (e.g., the bee, the moth, or the fly). Those randomly-acquiring mandibles strong enough to penetrate the stalk, acquiring nectar directly and in great quantity, would thus profit from "an accidental deviation in the size and form of the body." Furthermore, the more food acquired, the "better [the] chance of living & leaving descendants with a tendency to a similar slight deviation of structure" (222). According to Darwin's empirical vignettes, the survival or extinction of species ultimately depended on random phenotypic variations that provides advantages during the interactivities of diverse organisms (Urry 267).

From 1858 to 1876, Darwin's derived his understanding of natural selection from material evidence, recorded observations, and the research of naturalists, past and present. From this deposit of information, by 1858, he constructed the standard definition of natural selection that combined at least five propositions. On 31 March 1858, when he had completed the "Natural Selection" manuscript chapter, he articulated his first proposition: "All nature is bound together by an inextricable web of relation, if some forms become changed & make progress, those which are not modified or may be said to lag behind, will sooner or later perish" (NS, 272). In the 1859 or first edition of the Origin of Species, he correlated Malthusian population theory with several other ideas to complete his definition: all organic beings, of which more are born than can possibly survive, relate to each other and to their environments "in infinitely complex and close-fitting ways." Since Darwin inferred the existence of a hereditary mechanism from his close study of horticulture and animal breeding, he determined that physical variations useful to each individual in the struggle for survival tend to be preserved and inherited. Over the course of thousands of generations, advantageous variations in a stable ecosystem will promote adaptation, while maladapted forebears would become extinct (NS, 270-72; Origin of Species (1859) (80-81). Darwin's empirically-based illustrations, paraphrased above, make the process of natural selection intelligible to the general reader. They furnish pictorial analogues to a complex definition.

The Demiurgic Explanatory Narrative

In contrast to the empirical explanation, those which employ a Demiurge introduce it as the regulator of natural selection. Renamed a “Being” in the 1844 text, this entity directs the natural history of descent, adaptation, and diversity for all living forms (62-63). Darwin’s 1844 drafts asks the reader to “suppose” that the demiurgic Being discerns the innermost organization of living things, “imperceptible to man.” Along with its inward perceptiveness, this male Being possesses “forethought extending over future centuries” through which he selects offspring “with unerring care,” and with the capability of creating “a new race.” To accomplish this teleological end, the Being (“he”) chooses progeny (those bearing advantageous traits) to form one or more races and can segregate them on islands (e.g., as in the Galápagos chain), where his work further adapts creatures “to new ends.” The Demiurge's organic judgment, discrimination, forethought, and “steadiness of object” contrast with the judgment of the human breeder whose accretive development of traits breeds only commercially-profitable organisms. The beauty of the natural races that the Demiurge generates, in contrast, far surpasses the original stock and anything man can hope to achieve in domestic races. Under demiurgic agency, natural selection operates through the propagation of beneficial traits, not indirectly through the accumulation of effects over time, but through the agency of a prime mover whose consciousness transcends space and time.

The Demiurge of the 1844 sketch functions as a subordinate deity, neither self-sufficient nor omnipotent. Rather, organizing living forms as a kind of genetic engineer, “he” mediates between organisms, developing cross-breeds and inducing mutations. Hence, he will work on an organism’s “reproductive system,” keeping “its organization somewhat plastic,” so that, with time, further adaptations will be possible. The Being “might rationally . . . aim at almost any result,” provided “some unknown law” did not intervene; implicit limitations are imposed on his knowledge and power, as laws “unknown” to him prevent the survival of monstrosities.

To exemplify how this “imaginary Being” applies his power to an organism, Darwin presents the case of a stunted forest plant, growing on decaying matter and crowded by competing species (Foundations, 86-87). Through a hypothetical set of natural circumstances, the personified Being stimulates plant growth on the rotten stems of trees, setting into motion a chain of events to that end. The entity selects seedlings, the berries of which attract birds that consume and excrete the seeds widely. Concurrently, the Demiurge selects plants better able to draw nutriments from rotten wood, while destroying competitive seedlings, variants of the same species less able to draw moisture efficiently. The Demiurge may, over centuries, instill in the selected plant the capacity to survive on rotten wood, on the turf, and in the trees, wherever birds drop undigested seeds. By implication, the subordinate deity can enhance the survivability of the plant by modifying it and its environment so that it may thrive on recycled nutrients and minerals that saprotrophic organisms release through decomposition.

To enhance plant fertility, the Being selects seedlings with the taste of honey or pollen to attract insects for wider dissemination of seeds (Foundations, 86-87). If all of these measures “profited the plant,” he can render “different flowers” infertile through ongoing selection, thus eliminating competition. Overall, “he might aim at making a plant as wonderfully related to other organic beings, as is the mistletoe, whose existence absolutely depends on certain insects for impregnation, certain birds for transport[ation], and certain trees for growth.” Nor is it beyond the Being’s ken to adapt other organisms to the needs of the plant. Through selection, “our same Being” can modify the insect’s structure, “to facilitate the obtainment of honey or pollen.” The insect could, over generations, conform to the flower, as well-adapted progeny increase in number.

In the hypothetical passage above, Darwin portrays the biotic outcomes plausibly: how, through reciprocity, different Kingdoms can create conditions for a better adapted and more prosperous species of plant. Maladapted competitors become extinct in their niche while selected flora and fauna become mutually adapted to each other. However, the inconsistency is that Darwin attributes the engine and governance of the entire process to a semi-deified contriver rather than to an endogenous system of effects, which is precisely the way he would later define natural selection in 1859.

In the "Abstract of the Theory of Natural Selection sent to Asa Gray in 1857", Darwin reprised the character and work of the “imaginary Being” of 1844, who now becomes simply “a being” (with a lower-case b [Abstract], 153). Unlike the human breeder, the “being” of 1857 acts both on anatomy and physiology, both external and internal. A human breeder, on the other hand, is concerned with constitutional alterations only insofar as they produce commercially-preferred traits. The 1857 Demiurge bears supernal attributes: it never designs capriciously by propagating useless or freakish traits for the sake of novelty or profit. Unlike man who, in manipulating organic life for profit, is oblivious to unintended consequences, the natural principle, which the 1857 Demiurge applies with foresight, acts constantly over millennia and through generations. Further in the 1857 text, Darwin suggests that the Demiurge is independent of the phenomena it governs, being "at work on natural selection . . . which selects exclusively for the good of each organic being” (Abstract, 154).

In Darwin’s discussion of the principle of divergence in the manuscript written in 1856-1858, the Demiurge presides over the biosphere, implements natural selection, and is “not liable to caprice” (NS, 130-31). In the excerpt below, Darwin also includes God, the all-powerful Creator, in his system, but only as an after-thought. He writes that God had “ordained” the laws of nature to “govern” Creation. In Darwin's natural theology (or mythology), biodiversity and adaptation appear to have two motive sources: the aggregated laws of the Creator, by which Creation abides; and the direct action of a female entity, to whom is ascribed volition, rectitude, and constancy. Her intelligently-designed actions, which are inalterable and amoral, destroy the maladapted and preserve the survivors:

By nature, I mean the laws ordained by God to govern the universe [sentence added above original line of text (Stauffer p. 21)]. She cares not for external appearance; she may be said to scrutinize with a severe eye . . . the whole machinery of the organization. There will be no caprice, no favouring; the good will be preserved & the bad rigidly destroyed, for good & bad are all exposed during some period of growth or during some generation, to a severe struggle for life. Each being will live its full term & procreate its kind, according to its capacity to obtain food & escape danger. Nature will never select any modification without it giv[ing] some advantage to the selected being over its progenitors under the conditions to which it is exposed. [NS, 224-25]

This passage suggests that Darwin's cosmology belongs, in some respects, to the Deist tradition; and that the Demiurge may be an artifact of natural theology (Landow; Corey 6-27; Brooke 353).

The Demiurge: Survival & Extinction, 1860-1868

The final iteration of the Demiurge, previewed in the 12-15 June 1860 correspondence to Lyell and to John Dalton Hooker (1871-1911), is that of an Architect (DCP-LETT-2830, 2832, 2832A). In the literature of natural theology, the Architect usually refers to God; for example, the anatomist Richard Owen (1804-1892), in Archetypes and Homologies of the Vertebrate Skeleton, alludes to "the divine Architect building up certain of his diversified living works" (73). Darwin's version of the Architect, however, is a descendant of the demiurgic craftsman or Artificer (Greek: dêmiourgos), originating in Plato's Timaeus, and having variants throughout the Neo-Platonic and Gnostic traditions (Timaeus, 28a6, 87; Manier 153-54; La Vergata 938-41; O'brien 3-4).

Whereas Darwin had depicted the Demiurge in his early writings as a mundane efficient cause, by 1868, he realized that the struggle for survival depended on the "fluctuating variations of each organic being" (Variation, II: 514). The only missing explanatory component in Darwin's system was the mechanism itself, and pangenesis filled that theoretical void. In the passage below, the transcendental figure has gone, and a human architect, who is an ingenious planner, is simply compared to the principle, an efficient law of nature:

[I]f an architect were to rear a noble and commodious edifice, without the use of cut stone, by selecting from the fragments at the base of a precipice wedge-formed stones for his arches, elongated stones for his lintels, and flat stones for his roof, we should admire his skill and regard him as the paramount power. Now, the fragments of stone, though indispensable to the architect, bear to the edifice built by him the same relation which the fluctuating variations of each organic being bear to the varied and admirable structures ultimately acquired by its modified descendants. [Variation, II: 514]

The locus of activity and power, as the passage indicates, has moved away from the efficient cause and designer (the demiurgic Architect) to the principle of natural selection, a hypothetically-deduced system, the existence of which zoological, botanical, and geological evidence supported (Ghiselin 4, 63, 145-46, 195, 236).

Herbert Spencer, John Bagnold Burgess (1829-1897). 1872. Oil on canvas, 146 in. x 37 1/2 in. (1168 mm x 953 mm). National Portrait Gallery, London NPG 1358.

Herbert Spencer (1820-1903), who influenced Darwin's stylistic expression and conceptual development of natural selection, in the 1864 Principles of Biology incisively defines the idea and helped Darwin considerably. According to Spencer, natural selection is an indirect, pervasive, and equilibrating series of effects, one through which "plants may become better adapted, or readapted, to the aggregate of surrounding agencies, not through any direct action of such agencies upon them, but through their indirect action—through the destruction by them of the individuals which are least congruous with them, and the survival of those which are most congruous with them" (447). Spencer also contributed the modifying phrase, "survival of the fittest," to emphasize the capacity of natural selection to preserve so-called favored races in the struggle for life; moreover, he advised Darwin to include it in the 1869 fifth edition of the Origin of Species (447). Darwin took his advice, and the phrase "survival of the fittest" was introduced into that edition (Origin of Species, 91-2) (1869).

The reorientation of natural selection from the direct agency of the Demiurge to a network of equilibrating biotic effects appears in the excerpt from Variation quoted above, which identifies three centers of activity: geophysical forces of the rockfall, human artifice, and a hypothetical hereditary mechanism. Noticeably, the Demiurge has disappeared. According to this illustration, constant physical laws and an Intelligent overseer determines the random shapes of the fallen rocks and the geophysical energy involved in the avalanche; the human architect designs an edifice from natural materials, utilizing uneven fragments in the quarry; and randomly-acquired phenotypic variations determine the survivability of an organism under specific environmental conditions.

The one missing component of Darwin's evolutionary vision, the particulate theory of pangenesis, appears in the 1868 The Variation of Animals and Plants. Although eventually refuted, the theory of pangenesis held that "the whole organization, the sense of every separate atom or unit, reproduces itself"; hence, all reproductive units—"ovules and pollen grains, the fertilized seed or egg, as well as buds"—are made up of "a multitude of germs thrown off from each separate atom of the organism" (Variation, II: 429). As a hereditary mechanism, the ancestry of pangenesis is biological rather than demiurgic (II: 428-83; Guilizza). It is an integrated and unifying concept, connecting embryos to adults and species, linking sexual to asexual reproduction, and postulating an affinity between gametes and asexual buds (Mayr 693). In the concept of the gemmule, moreover, Darwin envisaged autonomous, mediatory particles involved in cellular reproduction and inheritance (Geison 377-78; Nyhart 209; Endersby 79). Despite its speculative character, the provisional theory departs from metaphysics and moves towards Mendelian genetics (Ghiselin 185; Geison 411; B. & D. Charlesworth 757-66).

In 1857, Abbot Gregor Mendel (1822-1884) began his heredity experiments using the pea plant. In 1860, while Darwin was contending with acerbic reactions to the Demiurge described in the 1859 edition of the Origin of Species, 960 miles east of Cambridge, in the City of Brno (now part of the Czech Republic), Mendel was discovering the laws of heredity; and, in 1867, a year before Darwin revealed his pangenesis theory, Mendel had published his theory of genetics. His great paper, "Experiments in Plant Hybridization," appeared in the 1865 Transactions of the Brünn Natural History Society (Mayr 714-22). In 1900, the Dutch botanist, Hugo M. De Vries (1871-1962), the German botanist Carl F. G. Correns (1864-1933), and the Austrian agronomist Erich von Tschermak-Seysenegg independently rediscovered Mendel's laws (Mayr 727-31). These great strides did not mean that Darwin's pangenesis theory had been stillborn. De Vries, for example, in the 1910 monograph, Intracellular Pangenesis, analyzed Darwin's theory, indicating his indebtedness to and departure from it. On a fundamental point, De Vries agreed with Darwin: "individual hereditary qualities are dependent on individual material bearers in the living substance of cells"; to describe these cellular particles, De Vries substituted the term, pangens, for Darwin's gemmules (215).

In The Descent of Man (2th edition, 1874), Darwin conjectures that, "the distinctive characteristics of man were the results of the [natural selection] principle"; however, since his theory of inheritance was provisional, he could only speculate on the generative force through which variations were produced (48, 61). In 1907, the evolutionary biologist and 1933 Nobel Prize winner in Physiology or Medicine, Thomas Hunt Morgan (1856-1945), elucidating the hereditary process, defined the roles of chromosomes and mutations. Darwin's personal milestone on the subject, reached in 1871, was to recognize natural selection to be "the chief agent of change" and a biochemically-activated principle, "largely aided by the inherited effects of habit, and slightly by the direct action of the surrounding conditions" (62).

When reflecting on the rhetorical paradox of the Origin of Species and related texts, Darwin did not acknowledge the Demiurge as having been a serious contradiction. He finds value in his having disproven the doctrine of Special Creation that, through divine fiat, all species were of independent origin and unchangeable: "if I have erred in giving natural selection great power, which I am very far from admitting, or in having exaggerated its power, which is in itself probable, I have at least . . . done good service in aiding to overthrow the dogma of separate creations" (The Descent of Man, 62). Although the dependence of natural selection on heredity was indisputable, as late as 1874, the mechanism of inheritance remained a mystery: "We know not what produces the numberless slight differences between the individuals of each species . . . each peculiarity must have had its efficient cause" (63).

Modern Commentators’ explanations of the Darwinian Demiurge

1. The demiurgic narratives are aesthetically appealing and even an instructional resource (Levine [2008], 246; A. C. Love);

2. The demiurgic narratives efficiently link metaphysical and physical aspects of Darwin's exposition (Beer [1983], 102; Kohn [1996], 14);

3. Natural selection is a "mental construct" and "exogenous power" (Guliuzza [2011a, 2011b];

4. The Demiurge is a place-holder for a particulate hereditary mechanism, essential to the complete understanding of Darwin's concept (Limoges 23-4; Manier 92-5; Beer [1983], 55, [1985], 562; LaVergata 939);

5. Natural selection, which the Demiurge governs, is a moral agency in human evolution (Richards 60-1, 64-6; Levine [2011], 87);

6. The figure of the Demiurge is superfluous to what is a predictable, algorithmic system (both "mindless" and "mechanical") (Dennett [1991], 8; [1995], 47-50, 60).

Works Cited

Beer, Gillian. Darwin's Plots: Evolutionary Narrative in Darwin, George Eliot and Nineteenth-Century Fiction. 1983. London: Routledge & Kegan Paul, 1985.

_____. "Darwin's Reading and the Fictions of Development." The Darwinian Heritage. Ed. David Kohn. Princeton, NJ: Princeton UP, 1985. 543-588.

Brooke, John Hedley. Science and Religion: Some Historical Perspectives. 1991. Cambridge: Cambridge UP, 2014.

Cain, Michael L. "The Evolution of Populations." Biology. By Neil A. Campbell, Jane B. Reece, Lisa A. Urry, et al. Ed. Beth Wilbur. 8th ed. San Francisco, Boston, New York: Pearson/Benjamin Cummings, 2009. 468-486.

Charlesworth, Bryan, and Deborah Charlesworth. "Darwin and Genetics." Genetics. (November, 2009) 183.3. Web. 4 June 2018.

Corey, Michael Anthony. Back to Darwin: The Scientific Case for Deistic Evolution. Latham, Massachusetts, New York, and London: Univ. Press of America, 1994.

Darwin, Charles. "Abstract of a Letter from C. Darwin, Esq., to Prof. Asa Gray, Boston, U.S., dated Down, September 5th, 1857. Part II of "On the Tendency of Species to form Varieties; and on the Perpetuation of Varieties and Species by Natural Means of Selection." By Charles Darwin, Esq., F.R.S., F.L.S., & F.G.S., and Alfred Wallace, Esq." Journal of the Proceedings of the Linnaean Society. Zoology. London: Longman, Brown, Green, Longmans & Roberts, and Williams and Norgate, 1858-1859. III, 50-53.

_____. The Foundations of the Origin of Species: Two Essays Written in 1842 and 1844. Ed. Francis Darwin. Cambridge: Cambridge UP, 1909.

_____, to Charles Lyell, 6 June 1860. Darwin Correspondence Project. "Letter no. 2822." http://www.darwin.project.ac.uk/. 10 August 2018.

_____, to J. D. Hooker, 12 June 1860. Darwin Correspondence Project. "Letter no. 2830." http://www.darwin.project.ac.uk/. August 2018.

_____, to Charles Lyell, 14 June 1860. Darwin Correspondence Project. "Letter no. 2832." http://www.darwin.project.ac.uk/.2 August 2018.

_____, to Charles Lyell, 17 June 1860. Darwin Correspondence Project, “Letter no. 2833.”http://www.darwinproject.ac.uk/. 9 August 2018.

_____, to Charles Lyell, 28 September 1860. Darwin Correspondence Project, "Letter no. 2931." http://www.darwin.project.ac.uk/. 16 August 2018.

_____. The Descent of Man and Selection in Relation to Sex. Ed. H. James Birx. 2nd ed. New York: Crowell, 1874; Amherst, New York: Prometheus Books, 1998.

_____. Natural Selection, Being the Second Part of His Big Species Book, 1856-1858. Ed. Robert C. Stauffer. 1975. Cambridge, Cambridge UP, 1989.

_____. On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life. 1st edition. London: John Murray, 1859.

_____. On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life. 2nd edition. New York: D. Appleton and Company, 1860.

_____. On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life. 3rd edition. London: John Murray, 1861.

_____. On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life. 4th edition. New York: D. Appleton, 1866.

_____. On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life. 5th edition. London: John Murray, 1869.

_____. On the Origin of Species by Means of Natural Selection or the Preservation of Favoured Races in the Struggle for Life. 6th edition. London: Odhams Press, 1872.

_____. On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life. 6th edition. New York: D. Appleton and Company, 1876.

_____. The Variation of Animals and Plants under Domestication. 2 vols. Vol. I. 1868. New York: D. Appleton and Company, 1900.

_____. The Variation of Animals and Plants under Domestication. Pref. Asa Gray. 2 vols. Vol. II. New York: Orange, Judd, & Company 1868.

Demiurge." Compact Edition of The Oxford English Dictionary. 2 vols. Oxford: At the Clarendon Press, 1971. Vol. I, A-O: 683.

Dennett, Daniel C. Consciousness Explained. New York, Boston, London: Little, Brown, and Company, 1991.

_____. Darwin's Dangerous Idea: Evolution and the Meaning of Life. New York: Simon & Schuster, 1995.

De Vries, Hugo. Intracellular Pangenesis, including a paper on Fertilization and Hybridization. Chicago: Open Court Publishing, 1910.

DuBois, Henry Augustus. Analysis of Darwin, Huxley and Lyell, Being a Critical Examination of the Views of These Authors in Regard to the Origin and Antiquity of Man. New Haven, Connecticut: Tuttle, Morehouse & Taylor, 1866. Victoria, Australia: Trieste Publishing, 2017. 1-30.

Dutta, A. C. Botany for Degree Students. Bombay, Calcutta, Madras: Oxford UP, 1968.

Endersby, Jim. "Darwin on generation, pangenesis and sexual selection." Cambridge Companion to Darwin. Eds. Jonathan Hodge and Gregory Radick. Cambridge: Cambridge UP, 2006. 69-91.

Geison, Gerald L. "Darwin and Heredity: The Evolution of His Hypothesis of Pangenesis." Journal of the History of Medicine and Allied Sciences. (October, 1969) 24.4: 375-411. U.S. National Library of Medicine. 6 April 2018.

Ghiselin, Michael T. The Triumph of the Darwinian Method. 1969. Mineola, New York: Dover Publications, Inc., 2003.

Guliuzza, Randy J. "Darwin's Sacred Imposter: How Natural Selection is Given Credit for Design in Nature." Acts & Facts. (2011); 40.7: 12-15. http://www.icr.org / 11 June 2018.

_____. "Darwin's Sacred Imposter: The Illusion That Natural Selection Operates on Organisms." Acts & Facts. (2011); 40.9: 12-15. http://.icr.org. /11 June 2018.

Kohn, David. "The Aesthetic Construction of Darwin's Theory." Ed. Alfred I. Tauber. The Elusive Synthesis: Aesthetics and Science. Boston Studies in the Philosophy of Science Series, vol. 182. Dordrecht, Boston, and London: Kluwer Academic Publishers, 1997. 13-48.

Landow, George P. "Darwin's views on religion: his agnosticism and his reasons for rejecting Christianity." Victorian Web. http://victorianweb.org / 16 April 2019.

La Vergata, Antonello. "Images of Darwin: A Historiographic Overview." The Darwinian Heritage. Edited by David Kohn. Princeton: Princeton Up, 1985. Pp. 938-941.

Levine, George. Darwin Loves You: Natural Selection and the Re-Enchantment of the World. Princeton, NJ, and Oxfordshire, UK: Princeton UP, 2008.

_____. Darwin the Writer. Oxford and New York: Oxford UP, 2011.

Limoges, Camille. La sélection naturelle: Étude sur le premiere constitution d'un concept (1837-1859). Histoire et Philosophie de la Biologie et de la Médicine. Paris: Presses Universitaires de France, 1970.

Love, Alan C. "Darwin's 'Imaginary Illustrations': Creatively Teaching Evolutionary Concepts & the Nature of Science." The American Biology Teacher. 72 (Feb. 2010): 82-89. Web. 12 April 2019.

Lyell, Charles, to Charles Darwin, 15 June 1860. Darwin Correspondence Project, “Letter, no. 2832A,” http://www.darwin.project.ac.uk./ 10 August 2018.

Manier, Edward. The Young Darwin and His Cultural Circle. Studies in the History of Modern Science, vol. 2. Dordrecht, Holland and Boston: D. Reidel Publishing Company, 1978.

Mayr, Ernst. The Growth of Biological Thought: Diversity, Evolution, and Inheritance. Cambridge, Massachusetts, and London: Harvard UP, 1982.

Mendel, Gregor. "Experiments in Plant Hybridization." Trans. William Bateson. Ed. Roger Blumberg. Transactions of the Brünn Natural History Society. (1865). Electronic Scholarly Publishing. www.esp.org./ 14 April 2017.

Moran, Thomas Hunt. Thomas H. Morgan — Biographical. Nobel.Prize.org. Nobel Media AB 2019.https://www.nobelprize.org/pries/medicine/1933/. 15 April 2019.

Müller, F. Max. Lectures on the Science of Language. 2 vols. 1863; London: Longmans, Green, and Company, 1885.

Nyhart, Lynn K. "Embryology and Morphology." The Cambridge Companion to the Origin of Species. Eds. Michael Ruse and Robert J. Richards. Cambridge and New York: Cambridge UP, 2009. 194-215.

O’brien, Carl Sean. The Demiurge in Ancient Thought: Secondary Gods and Divine Mediators. Cambridge and New York: Cambridge UP, 2015.

Owen, Richard. On the Archetype and Homologies of the Vertebrate Skeleton. London: John van Voorst, 1848.

"Pangenesis." Compact Edition of the Oxford English Dictionary. 2 vols. Oxford: At the Clarendon Press, 1971. Vol. II, P-Z, Supplement and Bibliography: p. 2065.

Plato. The Timaeus of Plato. Edited with Introduction and Notes by R. D. Archer-Hind. London and New York: Macmillan and Company, 1888.

Richards, Robert J. "Darwin's Theory of Natural Selection and Its Moral Purpose." The Cambridge Companion to the Origin of Species. 47-66.

Spencer, Herbert. The Principles of Biology. 2 vols. London and Edinburgh: Williams and Norgate, 1864.

Urry, Lisa A. "Mendel and the Gene Idea." Biology. Pp. 262-85.

Wollaston, Thomas Vernon. "Review of the Origin of Species." Annals and Magazine of Natural History. (1856) 5: 132-43.

Darwin and His Critics: The Reception of Darwin's Theory of Evolution by the Scientific Community. Ed. David L. Hull. Chicago and London: The University of Chicago Press, 1973. 126-41.

Last modified 25 April 2019