One in a zillion

How big is a zillion? "It's an extremely large, indeterminate number", Dictionary.com says. And how rare is an all-black penguin, rather than the black-and-white tuxedo-like colorings on most of the adorably big & wabbly birds? It's a one-in-a-zillion mutation, scientists say. On a recent trip for National Geographic Traveler magazine to the continent that is the world's southern tip -- Antarctica -- Contributing Editor Andrew Evans spotted one...