170 



NA'iURE 



[June 22, 1882 



years with wonderfully little practice, had played a tune 

 with no practice at all, he might truly be said to have 

 done so instinctively. But it would be a serious error to 

 suppose that the greater number of instincis have been 

 acquired by habit in one generation, and then transmitted 

 by inheritance to succeeding generations. It can be clearly 

 shown that the most wonderful instincts with which ue 

 are acquainted, namely, those of the hive-bee and of 

 many ants, could not possibly have been acquired by 

 habit. 1 



" It will be universally admitted that instincts are as 

 important as corporeal structures for the welfare of each 

 species, under its present conditions of life. Under 

 changed conditions of life, it is at least possible that 

 slight modifications of instinct might be profitable to a 

 species ; and if it can be shown that instincts do vary 

 ever so little, then I can see no difficulty in natural selec- 

 tion preserving and continually accumulating variations 

 of instinct to any extent that was profitable. It is thus, 

 I believe, that all the most complex and wonderful 

 instincts have originated." 



Briefly, then, in Mr. Darwin's view instincts may arise 

 by lapsing intelligence, by natural selection of accidental 

 and possibly non-intelligent variations of habit, or by 

 both principles combined — seeing that "a little dose of 

 judgment" is often commingled with even the most fixed 

 (or most strongly inherited) instincts. One good test of 

 the truth of the view as a whole is that which Mr. Darwin 

 has himself supplied — namely, searching through the 

 whole range of instincts to see whether any occur which 

 are either injurious to the animals exhibiting them, or 

 beneficial only to other animals. Now there is really no 

 authentic case of the former, and the latter are so few in 

 number that they may reasonably be regarded, either as 

 rudiments of instincts once useful (so analogous to the 

 human tail), or as still useful in some unobservable 

 manner (so analogous to the tail of the rattlesnake). The 

 case of aphides secreting honey-dew for the benefit of 

 ants occurred to Mr. Darwin as one which might be 

 adduced against his theory in this connection, and he 

 therefore made some experiments upon the subject, which 

 led him to conclude that "as the excretion is extremely 

 viscid, it is no doubt a convenience to the aphides to 

 have it removed ; therefore probably they do not excrete 

 solely for the good of the ants." 



A discussion of the variability of instinct, and of the 

 probability that variations should be inherited, leads him 

 to consider the important case of the apparent formation 

 of artificial instincts in our domestic dogs by continued 

 training with selection, and also the not less important 

 case of the effects produced upon natural instincts by the 

 long-continued change of environment to which other of 

 our domestic animals have been exposed. All the facts 

 adduced as resulting from these long-continued though 

 unintentional experiments by man, go to substantiate, in 

 a very unmistakable manner, the theory concerning the 

 origin and development of instincts which we are con- 

 sidering. The chapter concludes with a close considera- 

 tion of some of the more remarkable instincts which occur 

 in the animal kingdom, such as the parasitic instinct of 

 the cuckoo, the slave-making instinct of ants, and the 

 cell-making instinct of bees. A flood of light is thrown 



1 Because the individuals which exhibit them, beinc neuters, can never 

 have progeny. It is indeed surprising, as Mr. Darwin further 



previously "advanced this demonstrative case of neuter insects 

 against the well-known doctrine of inherited habit as advanced by 

 Lamarck." 



upon the latter, and the old-standing problem as to how 

 the bees have come to make their cells in the form which 

 requires the smallest amount of material for their con- 

 struction, while affording the largest capacity for purposes 

 of storage, is solved. 



From this brief account of the chapter on " Instinct," it 

 is evident that the new idea which it starts, and in several 

 directions elaborates, is an idea of immense importance 

 to psychology, and that the broad marks or general prin- 

 ciples laid down by it afford large scope for a further 

 filling in of numberless details by the attentive observa- 

 tion of facts. The phenomena of instinct, indeed, cease 

 to be rebellious to explanation, and range themselves in 

 orderly array under the flag of science. 



But not less important than the chapter on " Instinct '" 

 are the chapters in the " Descent of Man " on the mental 

 powers of man as compared with those of the lower ani- 

 mals, on the moral sense, and on the development ot 

 both during primaeval and civilised times. Our estimate 

 of the value of these chapters is so high that we gladly 

 endorse the opinion of the late Prof. Clifford — who was 

 no mean judge upon such matters — when he writes of 

 them as presenting to his mind " the simplest, and clearest, 

 and most profound philosophy that was ever written upon 

 this subject." As the three chapters together cover only 

 80 pages, it seems needless to render an abstract of them, 

 so we shall only observe that although it is easy to show 

 in them, as Mr. Mivart and others have shown, a want of 

 appreciation of technical terms, and even of Aristotelian 

 ideas, nowhere in the whole range of Mr. Darwin's writings 

 is his immense power of judicious generalisation more 

 conspicuously shown. So much is this the case that in 

 studying these chapters we have ourselves always felt 

 glad that Mr. Darwin was not the specialist in psychology 

 which some of his critics seem to suppose that he ought 

 to have been if he presumed to shake their science to its 

 base; had he been such a specialist the great sweep of 

 his thought might have been hindered by comparatively 

 immaterial details. 



Of the three chapters which we are considering, the 

 most important is the one on the moral sense. As he 

 himself says : — 



"This great question (the origin of the moral sense) 

 has been discussed by many writers of consummate 

 ability ; and my only excuse for touching upon it, is the 

 impossibility of here passing it over ; and because, so far 

 as I know, no one has approached it exclusively from the 

 side of natural history. The investigation possesses, also, 

 some independent interest, as an attempt to see how far 

 the study of the lower animals throws light on one of the 

 highest psychical faculties of man." 



The result of this investigation and study has been to 

 give, if not a new point of departure to the science of 

 ethics, at least a completely new conception as to the 

 origin of the faculties with which that science has to deal; 

 and without attempting to discuss the objections which 

 have been raised against the doctrine, or to enumerate 

 the points of contact between this doctrine and older 

 ethical theories — to neither of which undertakings would 

 our present space be adapted — we may say in general 

 that, as in the case of instinct, so in that of conscience, 

 we feel persuaded that Mr. Darwin's genius has been the 

 first to bring within the grasp of human understanding 



