Unlike humans, it will never tour Europe, visit the Taj Mahal, or climb the Rockies. In order to do that, one needs specialized muscle cells, rows and rows of them, aligned like stalks of wheat. The lower animals skitter, creep, or worm along, covering mere yards of turf. The higher ones hop and leap and gallop or, if winged, vault and soar and dive. Specialization makes the difference. Consider just one product of specialized cells, the organ of sight. As the husband of an eye surgeon, I hear often