570 Frofeasor C. Lloyd Morgan [Jan. 28, 



makes it very difficult to rear by hand some birds, sucb as plovers, 

 whose natural food, in due variety, is not readily obtainable. It must 

 be remembered, too, that under natural conditions the parent bird 

 calls the young and indicates with her beak the appropriate food; 

 and this appears to afford an additional stimulus to the act of pecking. 

 Pheasants and partridges seem to be more dependent on this parental 

 guidance than domestic chicks, and they are more easily reared when 

 they have somewhat older birds as models, whose pecking they may 

 imitate. Passing allusion may here be made to a type of instinctive 

 response in some respects intermediate between the upward gaping of 

 the jay and the downward pecking of the chick. It is seen in the 

 young moorhen, which pecks upwards at food held above it, and can- 

 not at first be induced to take any notice of food on the ground. 

 Under natural conditions it is fed by the parent, which holds the 

 food in her beak above the little bird as it floats on the water. 



We have, then, in these simple instinctive acts examples of behaviour 

 which is congenitally definite in type for each particular species ; of 

 actions which are the joint product of an internal factor, hunger, and 

 an external factor, sensory impressions; of complex modes of pro- 

 cedure which subserve certain vital needs of the organism. It should 

 be mentioned, however, that the relative definiteness of instinctive 

 responses has been subjected to criticism from a psychological source. 

 It has been urged that the nutritive instincts, the play instincts, the 

 parental instincts, those of self-preservation, and those concerned in 

 reproduction, are so varied and multifarious that definiteness is the 

 last thing that can be predicated of them. Varied and multifarious 

 they are indeed, and each of the groups above mentioned contains 

 many differing examples ; but that is because we are dealing with 

 comprehensive classes of instinctive behaviour. The fact that the 

 group of fishes includes organisms of such wide structural diversity 

 as the salmon, the globe fish, the eel and the sole, does not affect the 

 fact that these species have a relatively definite structure each after 

 his kind. It is only when we treat a group of fishes as if it were an 

 individual fish that we are troubled by iudefiniteness of structure. 

 And it is only when we deal with a group of instincts comprised 

 under a class-name as if it were a particular instinctive act, that we 

 fail to find that definiteness which to the naturalist is so remarkable. 

 From the physiological jDoint of view, instinctive procedure would 

 Beem to have its origin in an orderly group of outgoing neural dis- 

 charges from the central office of the nervous system, giving rise to a 

 definite set of muscular contractions. And this appears to have an 

 organic basis in a congenital preformation in the nervous centres, the 

 activity of which is called into play by incoming messages, both from 

 internal organs in a state of i^hysiological need, and from the external 

 world through the organs of special sense. The naturalist fixes his 

 attention chiefly on the visible behaviour, which is for him the 

 essential feature of the instinctive act. But in view of the require- 

 ments of psychological interpretation it is advisable to comprise under 



