60 THE AMERICAN NATURALIST. (VoL. XXXIII. 
tive forms of life, in which the activities common to them and the 
mature human subject have not been obscured by the counter-play of 
motives and restraints. Observations in both these fields are accu- 
mulating at an immensely rapid rate. Psychiatry has a literature of 
its own, while the index to works on hypnotism, hysteria, and allied 
states fills a volume of itself. One can scarcely take up a periodi- 
cal — popular or technically psychological — without running across 
either a monograph on this or that phase of child-study, or a notice 
of some new book on the subject. The habits and peculiarities of 
the lower species of animals, the character of their sense perceptions, 
and the nature of their intelligence have long been studied, but 
rather as classes apart from each other and from man, and not as 
members of a common genetic group. We need a truly comparative 
psychology, which, by diligent study of the psychic life of all orders 
accessible to observation, will seek to show us what the intimate 
nature of the process of mental development actually is, and to trace 
back the developed processes manifested in the higher species to 
their roots in the primitive forms of action and reaction which com- 
prise the mental activities of the more elementary forms of life. 
The reflex and subliminal regions of consciousness are full of 
unsolved problems; instincts, automatisms, whims, and idiosyn-’ 
crasies, and all such marginal phenomena are things out of the 
unplumbed depths of our nature upon which biological psychology 
is bound to pour a flood of light. We need a paleontology of the 
soul, and the only instrument at hand by which we can probe the 
region of its vanished growth is that of comparison with the activi- 
ties of those simpler forms which are now to be found in the child 
and the lower animal. The child is always with us, and it needs 
but patience and faithfulness of observation to exploit its nature; 
but for the study of lower forms of life we need laboratories, of 
which aquaria and vivaria are but the beginning, in which systematic 
observation of a wide variety of animal life shall be carried on. 
Already a move in this direction has been made by more than one 
university ; an increasing number of students are coming to us from 
zoological museums and laboratories, and many signs point to a 
rapid and extensive development of biological psychology. 
The work which the laboratory of biological psychology shall carry 
on more systematically and comprehensively, — the patient and sym- 
pathetic study of wild and domestic animals, vertebrate and inverte- 
brate alike, — has already assumed great importance at the hands of 
many individual investigators, who, like our author, look upon the 
