im [328] 



DARWIN AND HUMBOLDT. 



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 proba 

 bly 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 

 iiim to consider the important case of 

 the apparent formation of artificial 

 instincts in our domestic dogs by con- 

 tinued training with selection, and also 

 the not less important case of the 

 effects produced upon natural instincts 

 by the long-continued change of en- 

 vironment to wdrich 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 unmistaka- 

 ble manner, the theory concerning 

 the origin and development of in- 

 stincts which we are considering. 

 The chapter concludes with a close 

 consideration of some of the more 

 remarkable instincts which occur in 

 the animal kingdom, such as the par- 

 asitic instinct of the cuckoo, the slave- 

 making instinct of ants, and the cell- 

 making instinct of bees. A flood of 

 light is thrown 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 construc- 

 tion, while affording the largest ca- 

 pacity for purposes of storage, is solv- 

 ed. 



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 psy- 

 chology, aud that the broad marks or 

 general principles laid down by it 

 afford lai-ge scope for a further filling- 

 in of numberless details by the attent- 

 ive observation of facts. The phe- 



nomena of instinct, indeed, cease to 

 be rebellious to explanation, and 

 range themselves in orderly array 

 under the flag of science. 



But not less importaut 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 animals, on the 

 moral sense, and on the development 

 of both during primaeval and civilized 

 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 the subject." As 

 the three chapters together cover only 

 eighty 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 generalization more con- 

 spicuously shown. So much is this 

 the case, that in studying these chap- 

 ters we have om-selves 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 hinder- 

 ed by comparatively immaterial de- 

 tails. N 



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 abil- 

 ity; 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 



