554 



NATURE 



[April 14, 1898 



The following day, after they had eaten many edible 

 caterpillars, the cinnabars were again thrown to them, 

 but the lesson had now been learnt by nearly all. 



" One chick ran, but checked himself, and, without 

 touching the caterpillar, wiped his bill — a memory of the 

 nasty taste having been apparently suggested by associa- 

 tion at sight of the black-and-yellow caterpillar. Another 

 seized one, and dropped it at once. A third sub- 

 sequently approached a cinnabar as it crawled along, 

 gave the danger note, and ran off. . . . Similarly, 

 moorhen chicks rapidly discriminated between small 

 edible beetles and soldier beetles. Such discrimination 

 is, however, not congenital, but acquired." 



This last conclusion is of great importance for the 

 theory of warning colours. If each generation of 

 insect-eating animals has to learn for itself what is fit 

 and what unfit for food, the advantage of conspicuous- 

 ness to the unfit and of similarity in conspicuousness 

 becomes much greater than under a condition of in- 

 stinctive discrimination. On this point Lloyd Morgan's 

 numerous experiments seem to leave little doubt. 

 "... There does not appear to be any congenital and 

 instinctive avoidance of such caterpillars with warning 

 colours." Of the instinctive avoidance of distasteful 

 insects he says, " I have not found a single instance." 



The theory of mimicry, due to H. W. Bates, is also 

 supported by the behaviour of duckling and moorhen 

 chicks which would not touch drone-flies after having 

 been stung by a bee and a humble-bee respectively. 

 There was never any evidence of an instinctive know- 

 ledge of the hurtful nature of bees and wasps. A very 

 young bird, after being once stung, is shy for a long time 

 not only of bees, but of various kinds of insects. An 

 older one, after a similar experience, is in the main only 

 shy of the stinging insect and others that closely 

 resemble it. 



There is an interesting description of the manner in 

 which the excreta are prevented from fouling the nest, 

 being voided over the edge or carried away by the parent 

 birds. A friend of the author observed that the young 

 of swallows, 



" after being fed by their parents, were nudged and 

 pushed until they turned round and voided excrement, 

 which was immediately seized by the parent bird with 

 the tip of the beak, carried away, and dropped outside." 



When the present writer was a boy, he (together with 

 his father and sister) witnessed a proceeding on the part 

 of a parent thrush which made a very deep impression 

 upon him. The parent bird was seen to alight on the 

 edge of its nest, and thrust its beak into the gapmg bill 

 and deeply down into the throat of one of its young, and 

 draw forth a large black and white worm-shaped object 

 (apparently from i| to 2 inches in length), which it then 

 swallowed. The nest was only a few feet away, below 

 the window of a summer-house, which afforded a perfect 

 view of the performance. It is probable that the observ- 

 ation, which has been up to the present time unintelligible 

 to the writer and those friends whom he has consulted, 

 is to be explained as one form of an instinct of which 

 other forms are recorded here. 



The earliest activities in walking, diving, and flying 

 are described in a most interesting chapter which proves 

 the extraordinary congenital accuracy with which these 



NO. 1485. VOL. 57] 



complex associated movements are performed. It is 

 argued with great force that the opportunity of watching 

 the movements of older birds does not offer any sufficient 

 explanation of the precision with which they are per- 

 formed by the young for the first time. "Who ever 

 learnt to do a difficult thing, even passably well, by 

 merely watching it done superbly by another?" The 

 author's observations convincingly demonstrate the truth 

 of the same conclusion ; for he watched the first attempts 

 of this kind made by young birds hatched in an incubator. 

 In all these the earliest associated movements were 

 astonishingly accurate, and sometimes, as in the first 

 dive of a startled moorhen chick (p. 64), incapable of 

 further improvement. Speaking of this example the 

 author says, 



" though long deferred, here was the instinctive activity 

 in congenital purity and definiteness, and absolutely true 

 to type, for this was the very first time he had ever 

 dived, nor had he ever seen any bird do so." 



The precision and freedom with which swimming and 

 diving are first performed seems to be much greater than 

 that with which walking and flying are begun. It is not 

 improbable that the difference is due to the further 

 difficulty introduced by the necessity in the latter case, 

 and especially in that of flying, of sustaining the 

 weight of the body, and of starting and checking its 

 movements, for the first time. It is probably this, 

 rather than the coordination of muscular movement, 

 which explains such hesitation and such feebleness as is 

 at first observed. In other words it is probably the 

 considerable strain thrown upon the muscles for the first 

 time which prevents perfect precision, so that when 

 this additional strain of weight is borne by the water, 

 the accuracy of the earliest coordinated movements is 

 much greater. Nevertheless the example of the Mega- 

 podius, quoted on p. 76, renders it probable that the 

 movements of flight may be performed with complete 

 success immediately after hatching, when they are 

 necessary for the existence of the species. 



All these statements and arguments only refer to 

 the power of sustaining and moving the body in the air 

 under the most favourable conditions. For the count- 

 less adjustments to the ever-varying currents of wind, it 

 is held that very considerable individual practice is 

 necessary. Flight in its finished form is "the result 

 of practice and individual acquisition . . . founded on 

 a congenital basis " (p. 78). 



The conclusions to be drawn from many of these 

 observations on young birds are summed up in a most 

 interesting manner in Chapter iv. Thus, in the case of 

 the associated muscular movements referred to above, 

 "what is inherited is a congenital coordination of motor 

 responses under the appropriate conditions of stimulation. 

 Not only is there inherited a given structure of leg or 

 wing, but a nervous system through which there is an 

 automatic distribution of outgoing currents to the several 

 muscles concerned ; so that, without learning or ex- 

 perience, they are called into play with nicely graded 

 intensity, and exhibit complex contractions and re- 

 laxations in serial order, thus giving rise to instinctive 

 behaviour of an eminently adaptive nature." 



In feeding there is 

 "a similar congenital coordination of motor responses 

 for pecking at a small object within a suitable distance. 



