t, capricious and unsettled in his mental tastes and
inclinations, but had set his face steadily towards his future
life-work. It is interesting to compare the importance in Huxley's
life of the _Rattlesnake_ voyage with the importance in Darwin's life
of the voyage on the _Beagle_ undertaken some fifteen years earlier.
Huxley, when he started, was a young surgeon with a taste of a vague
kind for dissecting and for drawing the peculiarities of structure of
different animals revealed by the knife and the microscope. Day after
day, month after month, year after year, in the abundant leisure his
slight professional duties left him, he dissected and drew, dissected
and drew, animal after animal, as he got them from the dredge or
tow-net, or from the surface of the coral reefs. He was not in any
sense of the word a collecting naturalist. The identification and
naming of species interested him little. What he cared for was, he
tells us, "the architectural and engineering part of the business: the
working out of the wonderful unity of plan in the thousands and
thousands of divers living constructions, and the modifications of
similar apparatuses to serve different ends." And so, on the
_Rattlesnake_, and in his work in continuation of the _Rattlesnake_
investigations,--which occupied most of his time for a few years after
his return to London,--there was gradually growing up in his mind a
dim conception of the animal kingdom as a group of creatures, not
built on half a dozen or more separate plans or types, each
unconnected with the other, but as a varied set of modifications of a
single type.

When Darwin set out on the _Beagle_, unlike Huxley, he was an
enthusiastic collecting naturalist. He had wandered from county to
county in England adding new specimens to his collections of
butterflies and beetles. As the _Beagle_ went round the world visiting
remote islands, far from land in the centre of the waters,
archipelagoes of islands crowding together, islands hugging the shore
of continents, and the great continents of the old and new worlds, he
continued to collect and to classify. Gradually the resemblances and
differences between the creatures inhabiting different parts of the
earth began to strike him as exhibiting an orderly plan. He saw that
under apparently the same conditions of food and temperature and
moisture, in different parts of the world the genera and species were
different, and that they were most alike in re