Delbœuf has denied that this process ever involves any real metamorphosis of images; he regarded it as an illusion due to rapid succession of distinct images which are afterwards combined in memory. That view is not, however, tenable; apart from the fact that it makes the illegitimate assumption that our recollection of a dream is entirely unreliable, it must be remembered that (as Giessler has pointed out) the shock of emotional horror or surprise that frequently accompanies such dreams suffices to prove the reality of the metamorphosis. Thus I once, as a youth, had a vivid dream of an albatross that became transformed into a woman, the beautiful eyes of the albatross taking on a womanly expression, but the bird's beak only being imperfectly changed into a nose as the bird-woman murmured, 'Do you love me?' In this case the vivid surprise of the dream was precisely associated with the simultaneous existence of the two sets of characters. It is not, however, necessary that there should be any metamorphosis of dream images, nor even that the procession of dream imagery should be continuous. And whether or not there is metamorphosis of images, whether the imagery is continuous or discontinuous, it seems to me that we must admit the possibility of its spontaneous character. That is, indeed, a debated, and, it may be admitted, a debateable point. Thus Foucault[13] accounts for the multiplication of almost similar images sometimes witnessed in dreams as due to _desire;_ we see a number of things because we desire to possess a number of these things, and he explains a dream of Delbœuf's, of a procession of lizards, as due to the fact that Delbœuf was a collector of lizards, in the same way as he would explain the dreams of thirsty people who imagine they are drinking repeated glasses of water or wine. I am quite unable to accept this explanation. The shifting and multiplication of dream imagery, as in the procession of lizards, is a fundamental and elementary character of spontaneous mental imagery, and is constant in some drug visions, notably those occasioned by mescal.[14] The repetition of imaginary drinks in the dreams of a thirsty man belongs to another more special class in explanation of which desire may be more properly invoked; it is merely the expression of the fact that after the imaginary drink the dreamer remains thirsty, and the suggested image is therefore repeated.