Rouse, and others in this country is entirely unnoticed; as is also the work of Hess and others in Germany. Consequently, there is little in the chapter but references to anecdotal literature, largely to that of Romanes. It must be said in all fairness to the author that he fails to find in this anecdotal literature anything bearing upon the question of mind in birds. Had he been familiar with the American and German literature on bird life, however, he would not have found such a disparity in ability to learn and to 'imitate' between the birds and the mammals. The chapter on the mammal brain is also supported by Morgan's work, that of Hobhouse, and the one study of Thorndike, Animal Intelligence. He regrets the fact that Thorndike has never given us his promised study on the primates (Mental Life of Monkeys, Monograph Supplement, Psychological Review, 1901)! I cite these failures merely to show that the author has no scientific justification for undertaking to write about a subject with which he is so little acquainted.
To come to the author's contentions. He finds no justification for the modern notion of coupling intelligence with a trial and error type of learning He agrees with Weissmann's doctrine of unconscious thought, and finds in it an explanation of learning in most organisms below the mammals. We may form both conscious and unconscious associations. Learning can occur anyway in complex neural mechanisms (where the cortex is not highly elaborated) without any consciousness being present. He fails to come to close quarters with the question as to where mind first becomes apparent. He examines the various orders of animals and gives us in a summarized statement the following vague expressions: "The Protozoa and the Cœlenterates may be summarily dismissed. In the succeeding worlds of the Worms, Molluscs, Echinoderms and Crustacea few and slender claims are made for the presence of an agency other than that of their nervous mechanism." "There may be a dull glow of consciousness in the fish." With regard to the higher insects he is somewhat in doubt. "The only reliable (and still indirect) way to infer consciousness is from the structure of the brain, and the brain of the insect is so obscure, and so little analogous to that of man, that we can draw no confident conclusion." "The question remains whether the cerebral activities of the ant or the bee may not be accompanied with a dull glow of consciousness."
In the mammals we find our first advanced stage of consciousness. The author really attempts to make cortical differentiation the criterion of conscious development. All through his book he attempts to argue away from and to argue down the evidence from behavior where he fails to find a complex cortex. He does not show in any adequate way how the behavior of the simpler mammals differs from that of birds, fish, etc. His conclusion is really based upon structure.
He modestly leaves open the question of the ultimate nature of consciousness. He declines to see in it the emergence or accession of a new reality, "other than ether, or ether-compacted nerve." "Until we know the cortex sufficiently well to say that its structure throws no light on the nature of consciousness,
