"...a plant-animal symbiosis, drawing energy from its private thermonuclear sun, nourishment from the gas and stones of space." (pp. 149-150)
The ever-changing interior contains:
rich, strange odors;
complex patterns of resonant, sibilant tones;
alternating breezes and calm, dimness and brightness;
rippling, waste-absorbing decks;
passages expandable as rooms with temporarily grown furniture.
Outside the ship, the travelers see:
the "...hundred different umbers and rust-reds..." of Mars (p. 151);
"Jupiter, imperial world..." described in a poetic paragraph (p. 156);
the "...gigantic rainbows..." of Saturn's rings seen from below (p. 163);
Mercury, "...crags and craters under a black sky...pools of molten metal..." (p. 172);
"Sunward of Mercury...an unutterable white splendour..." (p. 174);
"(...[the Sigman] found Venus as unattractive at close quarters as men did.)" (p. 166)
The Sigmans have neither waged wars nor polluted their environment. The visiting Sigman seems to assume that humanity is as innocent as the few other races with atomic power that it has encountered. Has it found only innocent races because others have destroyed themselves? How will Sigman technology affect human society? I have yet to reread to the end of the novel...