norance. Some authors, for instance Dr.
Prosper Lucas, look at variability as a necessary contingent on
reproduction, and as much an aboriginal law, as growth or inheritance.
Others have of late encouraged, perhaps unintentionally, this view by
speaking of inheritance and variability as equal and antagonistic
principles. Pallas maintained, and he has had some followers, that
variability depends exclusively on the crossing of primordially distinct
forms. Other authors attribute the tendency to variability to an excess of
food, and with animals to an excess relatively to the amount of exercise
taken, or again to the effects of a more genial climate. That these causes
are all effective is highly probable. But we must, I think, take a broader
view, and conclude that organic beings, when subjected during several
generations to any change whatever in their conditions, tend to vary; the
kind of variation which ensues depending in a far higher degree on the
nature or constitution of the being, than on the nature of the changed
conditions. {251}

Those authors who believe that it is a law of nature that each individual
should differ in some slight degree from every other, may maintain,
apparently with truth, that this is the fact, not only with all
domesticated animals and cultivated plants, but likewise with all organic
beings in a state of nature. The Laplander by long practice knows and gives
a name to each reindeer, though, as Linnaeus remarks, "to distinguish one
from another among such multitudes was beyond my comprehension, for they
were like ants on an ant-hill." In Germany shepherds have won wagers by
recognising each sheep in a flock of a hundred, which they had never seen
until the previous fortnight. This power of discrimination, however, is as
nothing compared to that which some florists have acquired. Verlot mentions
a gardener who could distinguish 150 kinds of camellia, when not in flower;
and it has been positively asserted that the famous old Dutch florist
Voorhelm, who kept above 1200 varieties of the hyacinth, was hardly ever
deceived in knowing each variety by the bulb alone. Hence we must conclude
that the bulbs of the hyacinth and the branches and leaves of the camellia,
though appearing to an unpractised eye absolutely undistinguishable, yet
really differ.[603]

As Linnaeus has compared the reindeer in number to ants, I may add that
each ant knows its fellow of the same community. Several times I carried