The gyroid and Lidinoid are
triply periodic minimal surfaces of genus three embedded in R3 that contain no
straight lines or planar symmetry curves. They are the unique embedded members of
the associate families of the Schwarz P and H surfaces. We prove the existence of two
1-parameter families of embedded triply periodic minimal surfaces of genus three
that contain the gyroid and a single 1-parameter family that contains the
Lidinoid. We accomplish this by using the flat structures induced by the
holomorphic 1-forms Gdh, (1∕G)dh, and dh. An explicit parametrization of
the gyroid using theta functions enables us to find a curve of solutions in a
two-dimensional moduli space of flat structures by means of an intermediate value
argument.