ace, which make him seem like a mere bit of the shingle-strewn
rock on which he reposes. In short, where the environment is most
uniform the colouring follows suit: just in proportion as the
environment varies from place to place, the colouring must vary in order
to simulate it. There is a deep biological joy in the term
'environment'; it almost rivals the well-known consolatory properties of
that sweet word 'Mesopotamia.' 'Surroundings,' perhaps, would equally
well express the meaning, but then, as Mr. Wordsworth justly observes,
'the difference to me!'

Between England and the West Indies, about the time when one begins to
recover from the first bout of sea-sickness, we come upon a certain
sluggish tract of ocean, uninvaded by either Gulf Stream or arctic
current, but slowly stagnating in a sort of endless eddy of its own, and
known to sailors and books of physical geography as the Sargasso Sea.
The sargasso or floating seaweed from which it takes its poetical name
is a pretty yellow rootless alga, swimming in vast quantities on the
surface of the water, and covered with tiny bladder-like bodies which at
first sight might easily be mistaken for amber berries. If you drop a
bucket over the ship's side and pull up a tangled mass of this beautiful
seaweed, it will seem at first to be all plant alike; but, when you come
to examine its tangles closely, you will find that it simply swarms with
tiny crabs, fishes, and shrimps, all coloured so precisely to shade that
they look exactly like the sargasso itself. Here the colour about is
less uniform than in the arctic snows, but, so far as the
sargasso-haunting animals are concerned, it comes pretty much to the
same thing. The floating mass of weed is their whole world, and they
have had to accommodate themselves to its tawny hue under pain of death,
immediate and violent.

Caterpillars and butterflies often show us a further step in advance in
the direction of minute imitation of ordinary surroundings. Dr. Weismann
has published a very long and learned memoir, fraught with the best
German erudition and prolixity, upon this highly interesting and obscure
subject. As English readers, however, not unnaturally object to trudging
through a stout volume on the larva of the sphinx moth, conceived in the
spirit of those patriarchal ages of Hilpa and Shalum, when man lived to
nine hundred and ninety-nine years, and devoted a stray century or so
without stint to the work of education,