Material for this chapter

Like the rest of this book, this chapter is strongly based on my personal work and observations. For almost all of the systems discussed I have personally collected extensive data and samples, often over the course of many years, and sometimes in quite unlikely and amusing circumstances. I have also tried to study the existing scientific literature, and indeed in working on this chapter I have looked at many thousands of papers and books—even though the vast majority of them tend to ignore overall issues, and instead concentrate on details of often excruciating specificity.