LIMITS OF COMPARATIVE PSYCHOLOGY 721 



alleged necessity of explaining every phenomenon in the simplest 

 possible way. Now the physiological antecedent of a movement 

 has always to be admitted, so that the introduction of conscious- 

 ness as part-condition of a movement certainly adds a compli- 

 cating factor. It follows on this principle of parsimony that any 

 animal movement which can be explained as unconscious should be 

 so explained, in other words, that the simplicity of the unconscious 

 reflex conception gives it right of way. 



The empirical argument of the mechanists, against the continuity 

 theory, is in the main the development of a counter-analogy: the 

 likeness of the supposedly purposive and conscious acts of animals 

 with plant changes, and with mechanical processes. The argument 

 has three distinguishable forms. In the first place, it has been 

 experimentally demonstrated, by Loeb, Bethe, and others, that many 

 animal activities which have been called psychic are, in reality, 

 direct responses to mechanical, chemical, or electrical stimuli. 1 

 Even the home-seeking activity of ants, Bethe has shown, de- 

 pends on the traces of food which has been dropped on the out- 

 ward road. Bethe argues that the home-seeking is, therefore, an 

 unconscious reaction to a chemical stimulus. 2 



It has been shown by the mechanists, in the second place, that 

 instinctive animal activities, usually conceived as conscious on ac- 

 count of their purposive character. 3 are persisted in when they have 

 become useless, and even positively harmful. Loeb, for example, has 

 experimented on the crevice-crawling instinct of animals, 4 which is 

 usually cited as an activity performed for the purpose of self-pre- 

 servation, a movement to escape pursuit by seeking obscurity. Loeb, 

 however, finds by ingenious experiments on butterflies and on 

 worms, that the instinct persists when the crevice is brightly 

 lighted, and therefore at least unsuited for a place of concealment. 

 By similar experiments, Yerkes has shown that certain crustaceans 

 persist in a hurtful instinctive activity; 5 and Jennings has proved 

 the same for several forms of infusoria. 8 



1 Loeb lays great stress on the teaching that the nervous system, so far from 

 being functionally distinct from protoplasm, merely "plays the part of a more 

 sensitive and quicker conductor for the stimulus." This doctrine, though well 

 established (cf. Loeb, op. cit., pp. 4 seq., 38 et al., and Der Heliotropismus der 

 Thiere, Wiirzberg, 1890, sec. 69, and p. 113; Goltz u. Ewald, Pfliiger's Arch., LXIII, 

 p. 374, 1896; Schrader, Pfluger's Arch., XLII, 1887, pp. 75 seq., and XLIV, 

 1888, p. 175), has no direct bearing on the present discussion, except for those 

 who start from the a priori conviction that nerve-excitation is an inevitable and 

 theoretically necessary condition of consciousness. 



2 Pfliiger's Arch., LXX, pp. 15 seq., 1898. 



3 Cf. p. 724, below. 



4 Op. cit., pp. 184185. Cf. Der Heliotropismus der Thiere, p. 1. 



5 R. M. Yerkes, Reaction of Entomostraca to Stimulation by Light, ii, Reactions 

 of Daphnia and Cypris, Amer. Jour, of Physiology, vol. iv, p. 419, 1900. 



8 H. S. Jennings, Studies on Reactions to Stimuli in Unicellular Organisms, 

 ii, Amer. Jour, of Physiology, vol. n, p. 330, 1899. 



