This book comprises of two parts. In the first, theoretical one, we sketch the biological basis and origin of nervous systems and, based on that, move on to develop a theoretical model for our agent architecture. In the second, practical one, we design this architecture, with its components and their interactions, and experimentally evaluate it. We do this by placing a number of our agents in little game worlds and letting them compete: Who can collect the most food, escape predators best, and triumph over his competitors in a Darwinian struggle?