There is one idea included, if only partially expressed and exoteric in character, in that fundamental vision we have been discussing, which modern scientific thought might well find relatively little difficulty in assimilating: namely, that the acts of propagation by which a series of genetically connected individuals proceed one from another are not really an interruption but only a constriction of both bodily and spiritual life. Thus we can speak of the identity of an individual's consciousness with that of one of his ancestors in much the same sense as we can of the identity of my consciousness before and after a deep sleep. The usual argument against recognition of this fact is to point to the presence of memory in the one case and its ostensibly complete absence in the other. But today the recognition has surely, to a large extent, won through that, at least in the instincts of many animals, we are confronted by nothing less than supra-individual memory. Well-known examples include: the building of nests by birds, when the nest often exactly fits the size and number of eggs to be expected in this particular species, though there is no possibility of individual experience of this; then there is the ‘bed-making’ observed in many dogs, stamping down the grass of the steppes on the Persian carpet; and the efforts of cats to bury their excreta, even on wooden or stone floors, which obviously makes sense as a precaution against being smelt by an enemy or quarry.