42 SCIENCE AND PHILOSOPHY OF THE ORGANISM 



egg, react to the specific bodies forming their food or not. 

 Putting them in front of a dish which contained peas and 

 other small bodies of the most different kinds mixed together, 

 he saw them pick up these little bodies most accurately. 

 But they took all kinds of them, and experience alone taught 

 them to discriminate between what was food and what was 

 not. On the other hand, it had often been pointed out that 

 young poultry had an instinctive fear of the hawk and the 

 hawk's cry. Lloyd Morgan showed that young poultry are 

 frightened by any large body in motion and by any very 

 shrill sound. Thus these fine experiments teach us two 

 things : they teach us what simple and what individualised 

 stimuli are, and that, as far as experimentally ascertained, 

 only simple stimuli are the external stimuli of instincts. 

 Indeed, all cases of instincts which have been the subject 

 of experimental work hitherto have proved to be due 

 to simple external stimuli exclusively. The instinctive 

 antipathy between dog and cat is probably also the effect 

 of chemical compounds, of a " smell," if we choose to speak 

 a little less accurately, and not of an individualised stimulus, 

 not of the cat or the dog as being " seen." 



But the experiments about this important question are 

 not at all numerous, and it can by no means be categorically 

 asserted that instincts, in the true sense of the word, are 

 never called forth by a specific body which psychologically 

 would be called a " seen " one, 1 or, speaking more generally, 

 by a stimulus of the individualised type. 



1 Elise Hanel (Zeitschr. f. ally. Physiol. iv. 1904) has shown, following 

 the line of certain experiments of Ch. Darwin, that the earthworm reacts 

 specifically to the specific form of leaves or pieces of paper, always trying to 

 draw them into its tube-like cave by their most pointed edge ; the earthworm, 

 in fact, can be stimulated by a typical sequence of different singularities, 



