"[W]e realise... the fact and... reason for the diversity of animal behaviour. From the moment we regard evolution as... psychical transformation, we see... a multitude of forms of instincts each corresponding to a... solution of the problem of life. The 'psychical' make-up of an insect is not and cannot be that of a vertebrate ; nor can... [that] of a squirrel be that of a cat or... elephant: this in virtue of the position[s]... on the tree of life. ...[W]e begin to see ...a gradation formed. If instinct is a variable dimension, the instincts will... create, beneath their complexity, a growing system. They will form as a whole a... fan-like structure in which the higher terms on each nervure are recognised... by a greater range of choice and depending on a better defined centre of coordination and consciousness. ...The 'psychical' make-up of a dog... is... superior to that of a mole or a fish. ...[T]he upholders of the spiritual explanation have no need to be disconcerted when they see... in the higher animals (particularly in the great apes) ways and reactions which strangely recall... 'a reasoning soul'. If the story of life is no more than a movement of consciousness veiled by morphology, it is inevitable that... in the proximity of man, the 'psychical' make-ups seem to reach the borders of intelligence."