I have marked the copy, so that the reader can see at a glance what passages has been suppressed and where matter has been interpolated. I have also present a copy of “Erasmus Darwin.” I have marked this too, so that the genuine and spurious passages can be easily distinguished. I understand that both the “Erasmus Darwin” and the number of _Kosmos_ have been sent to the Keeper of Printed Books, with instructions that they shall be at once catalogued and made accessible to readers, and do not doubt that this will have been done before the present volume is published. The reader, therefore, who may be sufficiently interested in the matter to care to see exactly what has been done will now have an opportunity of doing so. _October_ 25, 1880. Chapter I Introduction—General ignorance on the subject of evolution at the time the “Origin of Species” was published in 1859. THERE are few things which strike us with more surprise, when we review the course taken by opinion in the last century, than the suddenness with which belief in witchcraft and demoniacal possession came to an end. This has been often remarked upon, but I am not acquainted with any record of the fact as it appeared to those under whose eyes the change was taking place, nor have I seen any contemporary explanation of the reasons which led to the apparently sudden overthrow of a belief which had seemed hitherto to be deeply rooted in the minds of almost all men. As a parallel to this, though in respect of the rapid spread of an opinion, and not its decadence, it is probable that those of our descendants who take an interest in ourselves will note the suddenness with which the theory of evolution, from having been generally ridiculed during a period of over a hundred years, came into popularity and almost universal acceptance among educated people.