The influence of history on the systematist is perhaps more beneficial. It provides a wonderful panorama of errors, pitfalls, biases, faulty theories, faulty practices — and some solid achievements. But in every age men have chuckled gently over the errors of the past while unconsciously committing those of the (then) present. Still, what can now be seen as wrong is, at least some of it, worth knowing, either in order to avoid the same errors ourselves (some of them may still be possible even within a very different conceptual framework), or to see how individuals have been influenced in their work and to try to analyse our own performances. Unfortunately, there is little evidence that knowing something of the past helps in any way to facilitate con structive action in the future; the best it can do is to warn us off some bad courses. The outstanding fact of biology is variation, at all levels from the individual up to the greatest groups. Ernst Mayr has a story somewhere of how depressed he was on conversing with a physicist of (fully-warran ted) world status to find that the great man could not think at all in terms of populations of individuals all at least some what different from each other — a commonplace in biology. To find order, pattern, definition in this amazing diversity has been one of the two greatest tasks of the biologist — he has had to learn to live with and handle variation, not of the math ematical sort completely analysable from a few basic premises, but of entities very imperfectly understood in themselves and of very dubious relationships to others. He has had to produce a taxonomy of unanalysed entities (Cain, 1958). Moreover, he has had to cope with variation produced in — from his own point of view — fundamentally different ways, not always distinguishable on his necessarily imperfect material. The wonder is, not that mistakes have been made, but that so much has been accomplished. It is true that human personality has intruded itself into the subject