A key element of Eugenides' writing style in Middlesex is interlocking, extended imagery and figurative language. Note the following example from Chapter 5, in which the factory assembly lines mirror the novel's ancestry imagery:
The Foundry is the deepest recess of the Rouge, its molten core, but the Line goes back farther than that. It extends outside to the hills of coal and coke; it goes to the river where freighters dock to unload the ore, at which point the Line becomes the river itself, snaking up to the north woods until it reaches its source, which is the earth itself, the limestone and sandstone therein; and then the Line leads back again, out of substrata to river to freighters and finally to the cranes, shovels, and furnaces where it is turned into molten steel and poured into molds, cooling and hardening into car parts [...].
In this excerpt, Cal/lie traces the production/assembly lines in Henry Ford's factories all the way back to their origins: out of Detroit and into the Great Lakes watershed, up north to the Upper Peninsula where raw materials are mined. In effect, Cal/lie traces the ancestry of each car, looking for clues about what it is within the raw materials used to produce it. Similarly, Cal/lie traces their own ancestry through "lines" in Middlesex, examining the raw genetic materials that comprise them. In order to neatly marry theme and symbolism in Middlesex, Eugenides includes many such meandering passages of extended imagery.