50 



NA TURE 



[NOVEMHEK 2 1 , I9OI 



before any occasion for its use has arisen. The relation 

 of body-cell to germ-cell in the struggle for existence 

 and in evolution is clearly explained in an admirable 

 comparison with the sterile and fertile individuals of the 

 hive. By this means two complex and difficult subjects 

 which have puzzled many a student of evolution are 

 together rendered easy of comprehension. 



The supposed cases of the instinctive hereditary fear of 

 the dog by the kitten, the hawk by the young turkey, &c., 

 are examined with much care in the chapter on conscious- 

 ness. This examination and the result of the author's 

 observations, together with those of Dr. Thorndike, Mr. 

 W. H. Hudson and Mr. Frank Finn, lead to the con- 

 clusion that an inherited timidity ready to find instant 

 expression at any unusual sight or sound has been 

 erroneously interpreted as the hereditary fear of certain 

 special enemies. 



The stages of the evolution of consciousness are 

 summed up in the statement that "in the first stage we 

 have consciousness as accompaniment ; in the second, 

 consciousness as guide ; in the third, consciousness as 

 judge." 



The term ins/hici is wisely limited to behaviour which 

 is independent of experience. Acts which, at first 

 voluntary, have become mechanical in the course of an 

 individual life are regarded as ac(]iiired habits, the popular 

 as well as the occasional scientific use of the term 

 instinctive for this purpose being rejected. The defi- 

 niteness of instinct is by no means held to imply that it is 

 rigidly the same in all individuals of a species. Indi- 

 vidual variation, bringing instinct under the sway of 

 natural selection, is freely admitted, as it was by both 

 Uarwin and Wallace in their joint essay in 1858. The 

 author's position in this respect is a return to the sound 

 principles first laid down by the great originators of the 

 theory of natural selection and a rejection of the attempt 

 to improve upon these principles by a widely different, 

 and for a time very popular, conception of instinct as due 

 to the hereditary transmission of the results of intelligent 

 learning, practice and habit, an interpretation which re- 

 ceivfed a fatal blow in Weismann's critical attack upon 

 the evidence in favour of the transmission of acquired 

 characters in general. The whole question is discussed 

 in an extremely fair and convincing manner in the section 

 on the evolution of instinct (pp. 106-116). 



The full definition of instinct which is here adopted 

 closely follows Dr. and Mrs. Peckham's summary of the 

 conclusions to which they were led by their deeply 

 interesting study of the solitary wasps. Instinctive 

 behaviour comprises 



"those complex groups of coordinated acts which are, 

 ell their first occurrence, independent of experience ; 

 which tend to the well-being of the individual and the 

 preservation of the race ; which are due to the co- 

 operation of external and internal stimuli ; which are 

 similarly performed by all members of the same more or 

 less restricted group of animals ; but which are subject 

 to variation, and to subsequent modification under the 

 guidance of experience" (p. 71). 



This is a definition which it is believed that Darwinian 

 naturalists in general will be prepared to accept, as well 

 as its application, e.f;., to the flight of birds where it is 

 inferred 



NO. 1673, VOL. 65] 



" that instinct provides a general ground plan of behaviour 

 which intelligent acquisition, by enforcing here and 

 checking there, perfects and guides to finer issues" 

 (p. 88). 



The whole section upon the instinctive behaviour of 

 young birds I'pp. 84-98) abounds in original observations 

 carefully carried out and interpreted with caution and 

 judgment ; they lead the author to the conclusion that 

 experience is not hereditary. 



The chapter on intelligent behaviour opens with the 

 discussion of simple examples which lead to the state- 

 ments that 



" whereas instinctive behaviour is prior to individual 

 experience, intelligent behaviour is the outcome and 

 product of such experience," 

 and again, 



" instinct depends on how the nervous system is built 

 through heredity ; while intelligence depends upon how 

 the nervous system is developed through use." 

 It may be doubted whether these sound and excellently 

 expressed principles are applied with sufficient rigidity to 

 the wonderful behaviour of insects. Thus Dr. and Mrs. 

 Peckham's observation of the use of a stone by the 

 solitary wasp Ammophila urnaria to beat down the 

 earth with which she was filling up the entrance of her 

 excavation is spoken of as " intelligent procedure," and 

 is referred to even more strongly in the words, "here we 

 have intelligent behaviour rising to a level to which 

 some would apply the term rational." And yet it is in 

 every way probable, in fact almost certain, that the whole 

 behaviour of the Anunnphila depended upon the manner 

 in which " the nervous system was built through heredity," 

 and that if the American naturalists had been fortunate 

 enough to witness the first performance of the wasp it 

 would have been found to be as perfect as any at 

 any later period in its life. It may be questioned whether 

 the use of the word "tool" is to be justified in speaking 

 of the employment of the fragment of stone. A "tool"' 

 is not any object which may be used for a purpose, but 

 an object fashioned for the purpose it is made to serve^ 

 a criticism which was suggested to the present writer by 

 Prof. E. Ray Lankester in a conversation about this very 

 observation. The use of decayed wood in the construction 

 of combs by many wasps is probably a more complex piece 

 of behaviour and more ditficult to understand as a pure 

 instinct than the behaviour of the Ammop/ii/a, and yet 

 in this case the interpretation is certain. The present 

 writer has seen the worker of a species of J'cspa freshlv 

 emerged from the pupa, and the sole perfect insect upon 

 the young comb (the queen mother having been previously 

 killed) immediately seize upon the broken material of the 

 comb and begin accurately and with exact precision to 

 build up the thin and delicate sides of injured cells 

 containing the living larva;. We may feel confident from 

 this fact that the worker possesses a nervous system which 

 impels it from the first to seek the right material and do 

 the highly complex work and enables it, without intelli- 

 gence, at the outset to make use of wood of the right 

 texture, dryness, &c. The use of stones, &c., for 

 closing the mouth of the burrow is probably as 

 ingrained in the nervous system o( A»!>iiop/iilaiLS the use 

 of wood in making cells is in the genus Vtspa. In addi- 

 tion to the observation of Dr. and Mrs. Peckham, we 



