vening Primrose among plants, and the
Fruit-fly, Drosophila, among animals, are well-known examples of
organisms which are at present in a sporting or mutating mood.

Certain dark varieties of moth, e.g. of the Peppered Moth, are taking
the place of the paler type in some parts of England, and the same is
true of some dark forms of Sugar-bird in the West Indian islands. Very
important is the piece of statistics worked out by Professor R. C.
Punnett, that "if a population contains .001 per cent of a new variety,
and if that variety has even a 5 per cent selection advantage over the
original form, the latter will almost completely disappear in less than
a hundred generations." This sort of thing has been going on all over
the world for untold ages, and the face of animate nature has
consequently changed.

We are impressed by striking novelties that crop up--a clever dwarf, a
musical genius, a calculating boy, a cock with a 10 ft. tail, a
"wonder-horse" with a mane reaching to the ground, a tailless cat, a
white blackbird, a copper beech, a Greater Celandine with much cut up
leaves; but this sort of mutation is common, and smaller, less brusque
variations are commoner still. _They form the raw materials of possible
evolution._ We are actually standing before an apparently inexhaustible
fountain of change. This is evolution going on.

The Sporting Jellyfish

It is of interest to consider a common animal like the jellyfish
Aurelia. It is admirably suited for a leisurely life in the open sea,
where it swims about by contracting its saucer-shaped body, thus driving
water out from its concavity. By means of millions of stinging cells on
its four frilled lips and on its marginal tentacles it is able to
paralyse and lasso minute crustaceans and the like, which it then wafts
into its mouth. It has a very eventful life-history, for it has in its
early youth to pass through a fixed stage, fastened to rock or seaweed,
but it is a successful animal, well suited for its habitat, and
practically cosmopolitan in its distribution. It is certainly an
old-established creature. Yet it is very variable in colour and in size,
and even in internal structure. Very often it is the size of a saucer or
a soup-plate, but giants over two feet in diameter are well known. Much
more important, however, than variation in colour and size are the
inborn changes in structure. Normally a jellyfish has its parts in four
or multiples of four. Thus it has