uncompleted at the time of his death in 1858. His monograph, describing
the fifty species then known, was published posthumously. Haeckel,
on whom the mantle of the great teacher was to fall, and who had been
Mueller's last pupil, took up the work his revered master had left
unfinished as his own first great original _Arbeit_. He went to Messina
and was delighted to find the sea there replete with radiolarians, of
which he was able to discover one or two new species almost every day,
until he had added one hundred and fifty all told to Mueller's list, or
more than triple the whole number previously known. The description of
these one hundred and fifty new radiolarians constituted Haeckel's first
great contribution to zoology, and won him his place as teacher at Jena
in 1861.

Henceforth Haeckel was, of course, known as the greatest authority
on this particular order of creatures. For this reason it was that
Professor Murray, the naturalist of the famous expedition which the
British government sent around the world in the ship _Challenger_,
asked Haeckel to work up the radiolarian material that had been gathered
during that voyage. Murray showed Haeckel a little bottle containing
water, with a deposit of seeming clay or mud in the bottom. "That
mud," he said, "was dredged up from the bottom of the ocean, and every
particle of it is the shell of a radiolarian." "Impossible," said
Haeckel. "Yet true," replied Murray, "as the microscope will soon prove
to you."

So it did, and Professor Haeckel spent twelve years examining that mud
under the microscope, with the result that, before he had done, he had
discovered no fewer than four thousand new species of radiolarians, all
of which, of course, had to be figured, described, and christened.
Think of baptizing four thousand creatures, finding a new, distinct, and
appropriate Latin name for each and every one, and that, too, when the
creatures themselves are of microscopic size, and the difference between
them often so slight that only the expert eye could detect it. Think,
too, of the deadly tedium of labor in detecting these differences,
in sketching them, and in writing out, to the length of three monster
volumes, technical dissertations upon them.

To the untechnical reader that must seem a deadly, a veritably
mind-sapping task. And such, indeed, it would prove to the average
zoologist. But with the mind of a Haeckel it is far otherwise. To him a
radiolarian, or any oth