  We have simulated two-colour four-flavour QCD at non-zero chemical potential
$\mu$ for quark number. Simulations were performed on $8^4$ and $12^3 \times
24$ lattices. Clear evidence was seen for the formation of a colourless diquark
condensate which breaks quark number spontaneously, for $\mu > \mu_c \sim
m_\pi/2$. The transition appears to be second order. We have measured the
spectrum of scalar and pseudoscalar bosons which shows clear evidence for the
expected Goldstone boson. Our results are in qualitative agreement with those
from effective Lagrangians for the potential Goldstone excitations of this
theory.
