In a simple sentence with very complex associations, Stephen considers fish feeding on the corpse of the drowned man: "God becomes man becomes fish becomes barnacle goose becomes featherbed mountain." The associative logic of the sentence is partly scientific, partly spiritualist, partly theological, partly legendary, partly erotic, partly mythographic—and fully poetic. Its emotional implications are largely positive.
The paragraph in which the sentence appears suggests a bleakly materialistic context for Stephen's thoughts: "Bag of corpsegas sopping in foul brine. A quiver of minnows, fat of a spongy titbit, flash through the slits of his buttoned trouserfly. . . . Dead breaths I living breathe, tread dead dust, devour a urinous offal from all dead. Hauled stark over the gunwale he breathes upward the stench of his green grave, his leprous nosehole snoring to the sun." Bodies decaying and bloating, infecting and consuming other bodies, excreting waste until they themselves become waste to be recycled by other organisms: these thoughts are consistent with the meditations on mortality that Stephen has conducted throughout the chapter, looking at broken seashells and dead dogs and recognizing their kinship with human beings. The animate no less than the inanimate world is an endless shuffling of essentially "dead" materials. Everything is in flux; no one survives the process of endless change. Leopold Bloom will think similar thoughts in Hades.
But life does persist, and it seems to obey—if only whimsically, fancifully—laws of metempsychosis and metamorphosis that Stephen has also been pondering throughout the chapter. A dog can transform before one's eyes into a hare, a horse, a deer, a bear, a cow, a wolf, a leopard, a panther, a vulture; waves appear to be walruses, serpents, and "the steeds of Mananaan." Human beings become rabbits or geese or pigeons. People may remember events from other lives many centuries earlier, or reincarnate figures like Moses in the bulrushes, the Israelites in Babylon, or Lady Macbeth. All of life seems to be bound together by principles of interpenetration that call into question the finality of death.
The Christian theology in which Stephen is steeped enters into his thinking: in the great mysterious act of Incarnation that transforms the immortal deity into mortal flesh, "God becomes man." And then, somewhat more fancifully, "man becomes fish" because early Christians anagrammatically associated their Savior with the Greek word for fish. The letters of Ichthys spell out Christ's essential names and properties: Iota initiates Iesous, Jesus; Chi begins Christos, the Messiah or anointed one; Theta invokes Theos, God; Ypsilon begins Yios, Son; and Sigma spells Soter, Savior. (It is perhaps not too ingenious to hear also in this phrase the ritual of Communion in which God gives himself to man to be eaten, for when Jesus performed miracles of feeding the hungry he gave them fish.)
Some geese do eat small fish, but the primary logic for the next transformation in Stephen's sentence is legendary. The "barnacle goose," a medium-sized species with distinctive black and white coloring on its head, got its name from a medieval theory that these birds do not procreate in the normal way. According to Gerald of Wales, writing in the Topographia Hiberniae (1187), barnacle geese "are produced from fir timber tossed along the sea, and are at first like gum. Afterwards they hang down by their beaks as if they were a seaweed attached to the timber, and are surrounded by shells in order to grow more freely. Having thus in process of time been clothed with a strong coat of feathers, they either fall into the water or fly freely away into the air. They derived their food and growth from the sap of the wood or from the sea, by a secret and most wonderful process of alimentation. I have frequently seen, with my own eyes, more than a thousand of these small bodies of birds, hanging down on the sea-shore from one piece of timber, enclosed in their shells, and already formed. They do not breed and lay eggs like other birds" (quoted from Edward Heron-Allen, Barnacles in Nature and Myth [1928, rpt. 2003], p. 10).
Fantastical as the ornithology may be, Gerald's description of the young birds' development does come pretty close to describing the domestic arrangement of barnacles, which attach to marine surfaces by their heads ("hang down by their beaks as if they were a seaweed"), grow thick shells as a protective home ("surrounded by shells in order to grow more freely"), and use their long delicate legs to trap food from the seawater and move it toward their mouths ("clothed with a strong coat of feathers"). It seems quite likely that Gerald's theory was based on close empirical observation of barnacles, but later writers elaborated more inventive accounts, as illustrated in the 16th century images here.
This medieval association between small sea creatures and a particular bird explains how "fish becomes barnacle goose." Stephen might have taken an interest in the legend not only because it was attached specifically to Ireland—for several centuries the Topography of Ireland gave other Europeans most of their information about that country—but also because churchmen squabbled for several centuries over whether the barnacle goose's unusual origins meant that it was really fish rather than flesh and therefore could be eaten on Fridays. This is the sort of rational theological absurdity that Stephen simply adores.
But Barnacle was also the surname of the woman whom James Joyce chose for his spouse: after meeting her, John Joyce ventured his opinion that "she will stick." This surname cannot be present in Stephen's consciousness, but he is walking on Sandymount Strand on 16 June 1904, the very day when Joyce walked out there with Nora and had a transformative sexual experience, and several paragraphs earlier he has been thinking, "Touch me. Soft eyes. Soft soft soft hand. I am lonely here. O, touch me soon, now," so the reader must suppose that the author intends to place Nora within his web of associations. With this added context, "barnacle goose becomes featherbed mountain" acquires distinctly erotic overtones. The feathers of dead geese are used to stuff a featherbed, and Nora too gets into that soft lovely bed.
All of these fanciful chains of association soften the brutally reductive vision of devouring a urinous offal from all dead. Summing them up, one might say that life reigns in the midst of death. And from this perspective, one can also note that the corpse on which Stephen is centering his speculations is not completely dead. The "quiver of minnows," darting like little arrows and flashing gleams of silver light, quiver with some of the life of the penis they have been snacking on. And the man's leprous nosehole is "snoring." In a strong anticipation of Finnegans Wake, this corpse may only be sleeping, and sleeping people merge with features of the landscape. Like Anna Livia "moananoaning" her "seasilt saltsick" way to the bay and HCE feeling his "humptyhillhead" in Howth and his "tumptytumtoes" at their "knock out in the park," this unconscious man has metamorphosed into the Featherbed Mountain.