We should in accordance with the Theory of Natural Selection expect to find traces of the ancestral form, not only in the lay-out of the adult animal, but in every phase of its life history, and that, in fact, is just what we do find. There is no more fascinating branch of comparative anatomy than embryology. Each life cycle we discuss tends to repeat the ancestral story, and only under the stress of necessity does it undergo modification at any point. There is little toleration in the life process for unnecessary divergencies. Economies are effected by short cuts and reductions, and special fœtal structures are granted reluctantly. So that even in man we find peeping through the adaptations imposed upon the human type by its viviparous necessities, and in spite of the advantage of every economy of force, memories, for example, of the gill slits, of the fish heart and kidney, of the reptilian skull, of the mammalian tail. I mention this fact in the _Outline_, and upon it Mr. Belloc comments in a manner that leaves one’s doubts poised between his honesty and his intelligence. He declares, which is totally untrue, that I “repeat the old Victorian tag”--I doubt if there ever was such a tag--that the embryo “climbs up the family tree.” He puts these words in inverted commas as though I have really adopted and used them, and for the life of me it is only by straining my charity to the utmost that I can accept that this was an accident. Of course every text-book of embryology for the last forty years has made it perfectly plain, as I have stated here, that the life cycle can be and is modified at any point, and that an embryo has much more serious work in hand than reciting its family history. It betrays its ancestral origins to analysis; but that is an altogether different matter. Mr. Belloc, however, is so densely ignorant himself upon these questions that he can imagine, or think it worth while to pretend to imagine and attempt to persuade his readers by the expedient of these inverted commas, that I entertain such a view. And then follow this, which I quote that the reader may the better understand a certain occasional acerbity in my allusions to Mr. Belloc:-- “He doesn’t know that Vailleton of Montpellier has knocked the last nail into the coffin of that facile and superficial Victorian shortcut (and blind alley). He has probably never heard of Vailleton, and when he does he will suspect him for a foreigner. That is what I mean by being provincial and not abreast of one’s time.”