mosfet - In an NMOS, does current flow from source to drain or vice-versa?

In an NMOS, does current flow from source to drain or vice-versa?

This Wikipedia page is confusing me: http://en.wikipedia.org/wiki/MOSFET

The above image confuses me. For the N-channel, it shows the diode's polarity going towards source in some, but away from the source in others.

I'm wondering which terminal should be connected to the power source (i.e. the positive battery terminal) and which should be connected to the power user (i.e. electric motor).

Answer

Conventional current flows from Drain to Source in an N Channel MOSFET.
The arrow shows body diode direction in a MOSFET with a parsitic diode between source and drain via the substrate. This diode is missing in silicon on saphire.

2a is a JFet so different topology.

2d is a MOSFET with no body diode. I've never seen one

\2e is a depletion mode FET - it is on with no gate voltage and takes negative voltage to turn the FET off. So diode has other polarity otherwise body diode would conduct whenever there was gate voltage.