A string of young ducklings as they sidle along through grass beside a
ditch—how like they are to a single serpent! I said in _Life and Habit_
that a colossal being, looking at the earth through a microscope, would
probably think the ants and flies of one year the same as those of the
preceding year. I should have added:—So we think we are composed of the
same cells from year to year, whereas in truth the cells are a succession
of generations. The most continuous, homogeneous things we know are only
like a lot of cow-bells on an alpine pasture.