"[DARYL started off as an]...off-the-shelf, $20 lexan kit
(made by Tamiya and marketed worldwide).  The $20 kit has a
molded lexan body shell and base, battery box, a momentary SPST
switch, and dual worm-gear DC motor drive.  The other photo is
of the very same WH Mouse kit but in a highly modifed form.  DARYL
mouse contains complex, additional, and completely original electronics
that I designed and built.

In my version, the original battery box was removed and replaced
by a 9V NiCad.  The single SPST switch was removed and replaced by
an array of haptic "whisker" sensors.  A battery voltage monitor
was added as was an RF radio signal strength converter and
wireless control link.  A full description of the, "different internal
structure[s]" appears at: http://www.maelzel.com/DARYL/HostDetail.htm .
If you're curious.

DARYL mouse cost nearly $2000 (if you include the mouse's brain
shown at:  http://www.maelzel.com/DARYL/Controller.htm and
described at: http://www.maelzel.com/DARYL/ControllerDetail.htm .
However, DARYL started out in life as a $20 Tamiya WH Mouse kit
from Edmund Scientific.  Thus, the obvious similarity.

I created DARYL, the artificial rodent, while completing my
masters in Electrical Engineering.  (Don't ask me why I nicknamed
the mouse project DARYL.  I'm not sure.  And, yes, I know there
was a movie with the same name.)  Actually, the whole experiment
came about as research in embodied, adaptive agent robotics
that was first suggested by the mathematician, Alan Turing.

The rodent's intelligence and learning engine were built solely
in adaptive, digital hardware - that is, DARYL has no processor
or code.  His "brain" is a single track P-Type Turing machine and
all of DARYL's adaptive traits and intelligent artifacts emerge from
EPLD/SRAM components (simulating "paper tape") mounted in the
controller, or brain, mentioned above.

In my experiment, the WH Mouse body was untethered and served as
the vehicle (host) to the embodied agent (intelligence).   The host
provided a physical platform capable of gathering sensory information
and of accepting returned agent behaviors (motor movements) back
through the agent's body and out into the world."