We have applied the name “systematics” or, if rationality is excluded, “classification” to all that part of a science which deals with diversities instead of generalities: in such a wide meaning systematics, of course, is not to be confused with that which is commonly called so in biology, and which describes only the exterior differences of form. Our systematics is one of the two chief parts of biology; what are called comparative anatomy and comparative embryology are its methods. For it must be well understood that these branches of research are only methods and are not sciences by themselves. *B.* THE THEORY OF DESCENT 1. GENERALITIES It is most generally conceded at the present time that the actually existing state of all organisms whatsoever is the result of their history. What does that mean? What are the foundations upon which the assumption rests? What is the relation of systematics to history? In raising such questions and considerations we are treading the ground sacred to the theory of descent. I well know that you prefer the name “theory of evolution” for what I am speaking of: but it may be misleading in various respects. We already know that quite a determinate meaning has been given to the word “evolutio” as applied to individual morphogenesis, “evolutio” being here opposed to “epigenesis.” Now there would be nothing against the use of the word evolution in a wider sense--indeed it is often applied nowadays to denote the fact that a something is actually “evolved” in embryology--if only our entelechy had taken the place of the machine of the mechanists. But that is the very point: there must be a real “evolving” of a something, in order that the word evolution may be justified verbally: and that is not the case in so-called phylogeny. At least we know nothing of an evolutionary character in the problematic pedigree of the organisms, as we shall see more fully hereafter. The term “theory of descent” is therefore less open to objection than is the usual English term. The word transformism, as used by the French, would also be a very good title. The theory of descent is the hypothetic statement that the organisms are really allied by blood among each other, in spite of their diversities.[143] The question about their so-called monophyletic or polyphyletic origin is of secondary importance compared with the statement of relationship in general.