, it was only a day or two before the date set for his
departure, and Colin was on the point of starting for Washington, when
he received a letter ordering him to his post on the Mississippi
immediately. He took the next train, and reported two days later at the
hatchery.

"Are you coming for any special line of work?" the superintendent asked
him. "I was informed from Washington that you were coming, but nothing
was said as to the nature of your duties."

"Nothing more than that Dr. Crafts said I should probably be working on
mussels, sir," the boy answered. "I was just told to report."

"The Deputy Commissioner states," the superintendent continued, looking
over the letter, "that you expect to join the Bureau permanently, and
that you have been doing some work at college on fishes."

"I haven't done very much, as yet, sir."

"I suppose not. But I want to find out what you know about mussels."

This put the boy on his mettle.

Colin told briefly, but quite clearly, what he remembered of the
life-history of the fresh-water mussel as described in the Bulletin that
had been given him, and added the information he had secured from the
Deputy Commissioner. The superintendent of the station put a few leading
questions to him, and nodded his head with satisfaction.

"So far as theory goes," he said, "I think you have a fairly good idea
of it, although here and there you made some statements showing the need
of a good deal of practical work with mussels. But, since you seem to
have a general idea of the anatomy and physiology, I think I will put
you in as Dr. Edelstein's assistant."

"What is he doing, sir?" queried Colin.

"He is working on pearl formations," was the answer. "You have heard, I
suppose, that there has been some excitement over pearl finds?"

"Yes, I heard that away up in Maine," the boy replied.

"It's exaggerated a good deal," the superintendent said; "but as a
matter of fact, there have been a few good finds. Dr. Edelstein is
studying the differences between oyster and mussel pearls. Of course,
when one of these 'rushes' comes, a very large number of inferior pearls
are found, which are of no commercial value but which afford good
material to work on. Just now," he added, "I think it is the most
interesting part of the work. Come along, and I'll introduce you to Dr.
Edelstein."

Colin's new chief was an entirely different type from any of the
scientists whom he had met in the Bureau. In the fi