The literature of animal psychology immedi ately after Darwin is characterized by a mass of observations industriously collected hut un fortunately not tempered by eareful and •onser vative interpretation. There was a marked ten dency to write in anecdotal vein of the doings of pet animals. and an equally marked tendency to that of animal capacity which we have mentioned above. Romanes and Lindsay may he taken as typical of this period. Re, ent literature attempts a more rigid application of experimental methods. The majority of present day investigators bring their animals into the laboratory, endeavoring in this way, even at the risk of artificiality, to standardize conditions and to secure the possibility of varying at will the environmental factors which control organic life. This method of procedure finds its most obvious application in the ease of those lower forms whose life history can be followed only with difficulty. if at all, in the natural state.
The reactions of micro-organisms. e.g., to me chanical, chemical, and thermal stimuli, have been studied beneath the microscope by numerous observers. And the results of investigation upon these minute unicellular forms, carried out by Gruber. Verwo•n, 31ffidus. Balbiani, and others, have had an important bearing upon that inter esting and fundamental question of animal psy chology. the origin of mind at large. Billet, reviewing the work of these authors, writes as follows: "If the existence of psychological phe nomena in lower organisms is denied, it will he necessary to assume that these phenomena can be snperadded in the course of evolution, in pro po•tion as an organism grows more perfect and complex. Nothing could be more inconsistent with the teachings of general physiology, which shows us that all vital phenomena are already present in undifferentiated cells. Furthermore, it is interestino• to note to what conclusion the admission would lead . . . that psychological properties are wanting in beings of a low order, and appear at different stages of zotilogical evolu tion. Romams has minutely particularized, on a large chart. the development of the intellectual powers, hut it is done in quite an arbitrary manner. According to his scheme, only proto plasmic movements and the property of excitabil ity are present in organisms of the lower class. Memory begins with the echinoderms: the pri mary instincts with the larva of insects and the annelids; the secondary instincts with insects end spiders: and, finally, reason appears with the higher crustaceans. I do not hesitate to say that all this laborious classification is artificial in the extreme, and perfectly anomalous." For
instance. "Bomanes assigns the first manifesta tions of surprise and fear to the larva' of insects and to the annelids. We may reply upon this point, that there is not a single infusorian that cannot be frightened, and that does not show its fear by a rapid flight through the liquid of the preparation. If a drop of acetic acid be intro duced beneath the glass slide in a preparation containing a quantity of infusoria, the animals will be seen to tly at once and from all directions, like a flock of frightened sheep." Binet 's fundamental thought is probably sound: his estimation of the infusorian conscious. ness is probably exaggerated. ,Tenning,s, e.g., ar gues from a very careful study of the paramecium, one of the protozoa, that the organism, if we may judge by its reactions, stands at the very bottom of the psychological scale. "We have in this animal perhaps as near an approach to the the oretical reaction postulated by Spencer and Bain for a primitive organism—namely. random move ment in response to any stimulus—as is likely to be found in any living organism." All the activities of the paramecium can be accounted for by "simple irritability, or the property of re sponding to a stimulus by a fixed set of move ments." Even more interesting, and fully as convincing,, are the inferences drawn by Bettie from his study of ants and bees. We are accus tomed to rank these creatures very high in the mental scale; but all Bethe's evidence goes to show that they are practically automata. Their remarkably complicated activities must, then, be regarded as purely physiological and uncon scious reactions to environmental changes. A typical experiment will illustrate the nature of the evidence collected, and will serve, at the same time, to contrast the results of the experi mental method with the results of simple obser vation. Huber, an enthusiastic observer of the habits of ants, noted that an ant which is taken from a nest and returned to it after an interval of four months is recognized and received by its former companions with all marks of friendli ness. Huber considered that this was good proof of the accuracy and permanence of the ant memory. Bettie. however, took an ant from a strange nest, dipped it in a mess of impounded "home" ants, and found that the disguised stranger was received with every token of recog nition and hospitality! The entire process of "recognition" is this explicable on the ground of a chemo-reflex. We shall see presently how this and similar results are to be reconciled with those which tell strongly for the existence of mentality in the forms of animal life.