We show that, when a solid semiconductor is heated, a thermoelectric instability can arise in the electron-hole gas (a liquid with two types of carriers). A dissipative relaxation mechanism can be added to the excitation. Creation of cellular motion is aided by an anisotropy corresponding to the large magnitudes of the gas characteristics in the heat flow direction. We derive the criteria for cell excitations and expressions for their dimensions when they first appear. We consider possible experiments and estimate the magnitudes of the effects sought.