In Brave New World, why is the Director is leading the students through the Hatchery?

There are at least two levels on which one can answer this
question.

First, on the literal level, the Director is
leading the students through the Hatchery so that they can get an overview of the
process of creating new life in this society.  He tells them that this is their one
chance to get a sort of overview of the general proces.  After that, they will be
involved in the details of their training.

Second, though,
we need to look at why Huxley would have this as the first scene of the book.  I would
argue that he does so to give us a quick (and somewhat shocking) view of how different
this "brave new world" really is.  As the Director leads the students through the
Hatchery, we learn about how there is no longer natural reproduction.  We learn how
proud they are of their scientific ability to totally remake the world.  We learn that
the whole point of their society is to create stability.  All of these things are
important things to know about this society.  By starting the book with this tour,
Huxley introduces us to these very basic and important facts about the society in this
world.