The classification of survivals in folklore into tribal and non-tribal items is a lengthy and intricate process. Some years ago I made a start in a study of fire worship which I presented to the British Association,[443] and I hope shortly to be ready with a volume on _Tribal Custom_, which will embody a fuller study of fire worship and its accompanying beliefs, together with a complete study of all the remains of traditional custom, rite, and belief, which only as the detritus of the ancient tribal organisation receive adequate explanation of their presence in the midst of modern political and religious institutions. If I leave this part of my subject without further illustration in this present volume, I must add one important note upon the persistence of survivals of both kinless and kinship societies. I have shown that the tribal system of the advanced races included provision for non-tribesmen, provision which kept non-tribesmen outside the tribal bond, and at the same time kept them tied to the tribe by using them as the necessary dependent adjunct of the tribe, using them as bondmen and serfs in point of fact. This extremely important factor in the history of the tribal organisation, which has not been properly noticed by the few authorities who have investigated tribal institutions, receives additional importance when viewed from the standpoint of folklore, for it allows for the preservation of non-tribal cults side by side with tribal cults. Non-tribesmen preserved their custom, belief, and rite simply because they were not admitted to the custom, belief, and rite of the tribe, and this is the explanation of the existence, in survival, of folklore which goes back to pre-Celtic times. Some of this pre-Celtic folklore we have already had before us, and some of it I have studied in my _Ethnology in Folklore_. Later on I shall have something more to say on the subject. Here it is only necessary to emphasise the importance of having ascertained why it is that the Celtic conquerors of Britain and the earliest tribal conquerors of the Indo-European world generally permitted to live in their midst what in a sense was opposed to all that they believed, to all that they practised, to all that governed them in thought and action.