  We reconsider the problem of the anomalous Hall effect in ferromagnetic
SrRuO$_3$, incorporating insights from the recently developed theory of Weyl
semimetals. We demonstrate that SrRuO$_3$ possesses a large number of Weyl
nodes, separated in momentum space, in its bandstructure. While the nodes
normally do not coincide with the Fermi energy, unless the material is doped,
we show that even the nodes inside the Fermi sea have a significant effect on
the physical properties of the material. In particular, we show that the common
belief that (non-quantized part of) the intrinsic anomalous Hall conductivity
of a ferromagnetic metal is entirely a Fermi surface property, is incorrect:
there generally exists a contribution to the anomalous Hall conductivity that
arises from topological Fermi-arc surface states, associated with the Weyl
nodes, which is of the same order of magnitude as the Fermi surface
contribution.
