Early on in the novel a distinction between the two families from which Tom and Maggie are descended is drawn out. The Dodsons are socially respectable, concerned with codes of behavior, and materialistic. The Tullivers are less socially respectable and have a depth of emotion and affection. The constant repetition of the characteristics of the two clans serves to create a division along which Maggie's and Tom's growth can be tracked. Tom is associated with the Dodsons, even more so when an adult, and Maggie is associated with the Tullivers.
We often see Maggie nearly lose consciousness when listening to music; she is so overcome with emotion and forgetful of any punitive or self-denying impulses. As a motif, music works the opposite way too: when Maggie experiences moments of profound, unconscious discovery or understanding, these moments are accompanied by a sense of music, as when she reads Thomas a Kempis for the first time and feels as though she hears, "a strain of solemn music." The vulnerability that Maggie experiences in relation to music can also put her in danger. Stephen Guest woos Maggie with music, not with words, and we see that his singing creates an "emotion that seemed to make her at once strong and weak: strong for all enjoyment, weak for all resistence." Music in The Mill on the Floss is not meant to indicate moments when Maggie is either succumbing to evil or experiencing good, but rather it indicates her generally heightened sensibilities—Maggie seems to experience everything with more emotion than others, and music is used throughout the novel to underscore this effect.
Especially in the early books of The Mill on the Floss, Tom, and especially Maggie, are associated with animal imagery. The imagery is usually of farm-type animals—ponies, dogs, ducks—and usually points to the character's capacity for affection or non-adherence to social convention. Following Darwin, Eliot uses this imagery also to gesture toward the wider relation between humans and animals that can be especially seen in young children. Thus, when Maggie and Tom reconcile in Chapter IV of Book First, the narrator points out, "We [adults] no longer approximate in our behaviour to the mere impulsiveness of the lower animals, but conduct ourselves in every respect like members of a highly civilized society. Maggie and Tom were still very much like young animals."
The motif of darkness and lightness of women—meaning their eyes, hair, or skin—is often used to emphasize the uniqueness of Maggie's appearance. The motif of darkness and lightness connects to the motif of the distinctions between the Dodsons and the Tullivers—the Tullivers have darker skin, while the Dodsons have lighter skin. The Dodsons, and indeed, all of St. Ogg's, respect or covet Lucy Deane's fair appearance. Her lightness is also prized in a larger cultural arena, and, in Book Fourth, Maggie becomes frustrated by the traditional plot lines in which the light, blond women live happily ever after in love. Maggie's family views her darkness as ugly and unnatural, yet by the end of the novel, it has made men perceive Maggie as more beautiful because her darkness is a rarity.