A Final Comment on Invertebrate Immunity
It is often assumed that we know enough about the immune mechanisms of animals to arrange them in linear sequence from the first eukaryote cell through to man. There is no compelling reason to believe that this is true. The underlying assumption made is that protective devices found in one group are elaborated in the next, more complex group. This is not true for other homeostatic devices, and the evidence available now does not support the notion that there has been straight-line evolution of immune mechanisms. Invertebrates have been around longer than vertebrates and have found a variety of solutions to common problems in the course of their evolutionary histories. The findings reported in this volume support this contention.