WASHINGTON—President Bush collapsed to the floor of the Oval Office during a meeting with advisers when spiderlings hatched from thousands of egg sacs affixed between the hemispheres of his brain, according to a White House memo released Monday. The spiders severed the president's corpus callosum and ate through the motor-control center of the brain, doctors said, causing Bush's body to jerk involuntarily as a scurrying mass of crab spiders emerged from his mouth and crawled down his face. Witnesses confirmed that a number of spiders also discharged from the president's tear ducts. Secret Service agents restrained the president and carried him to the White House medical facility, but doctors said that by the time Bush arrived, the arachnids had already consumed his corneas, pupils, and vitreous humor. Bush is resting comfortably at Bethesda Naval Hospital.