586 THE POPULAR SCIENCE MONTHLY. 



in the destruction of those in which it is imperfectly or abnormally 

 developed, and the preservation of those individuals which exhibit 

 any advantageous variation. 



In order to place the phenomena of instinct upon the same footing, 

 with reference to natural selection, as is held by other manifestations 

 of life, it is only necessary to show that instincts vary, and that these 

 variations may become hereditary. 



Not a great many years ago the statement that instinct varies 

 among animals of the same species would have been met by a flat 

 denial, but no one at all acquainted with the subject would probably 

 now be found to disj)ute it. A fcAV examples may not be out of place, 

 however. 



The oriole now builds its hanging-nest with the pieces of string, 

 horse-hair, yarn, and carpet-ravelings, which are to be found in abun- 

 dance about houses and barns ; and I have seen a nest into which 

 three fish-lines, with their hooks and sinkers, several yards of kite-tail 

 from a telegraph wire, and a shoe-string, were interwoven. Of course, 

 it is not natural for the bird to use such material as this, but the odds 

 and ends furnished by man are much better fitted to its needs than 

 the grass and fibres used by its less civilized ancestors. This change 

 certainly shows power to improve in accordance with changed condi- 

 tions ; but it may perhaps be said that it is not an example of change 

 in an instinct, but simply in a non-hereditary habit. The fear of man, 

 shown by almost all the smaller animals, is in many cases newly 

 acquired, for in regions uninhabited by man it is not shown, and it is 

 only as the animals of such regions learn, by generations of persecu- 

 tion, that man is highly and peculiarly dangerous, that they come to 

 avoid him ; yet this fear is truly instinctive, for it is shown by the 

 ^'oung as well as by the adult. The testimony of travelers as to the 

 tameness of animals in regions where they have never been persecuted, 

 is well known. For instance, Darwin, in his " Journal " of the voyage 

 of the Beagle, says : ".This disposition is common to all the terres- 

 trial species of the Galapagos Islands, namely, to the mocking-thrush, 

 the finches, wrens, tyrant fly-catchers, the dove, and carrion-buzzard. 

 All of them often a^^proached sufiiciently near to be killed with a 

 switch, and sometimes, as I myself tried, with a cap or hat. A gun 

 here is almost superfluous, for with the muzzle I jDushed a hawk oflT 

 the branch of a tree. One day, while lying down, a mocking-thrush 

 alighted on the edge of a pitcher made of the shell of a tortoise, 

 which I held in my hand, and began very quietly to sip the water ; 

 it allowed me to lift it from the gi-ound, while seated on the vessel. 

 I often tried and very nearly succeeded in catching these birds by 

 their legs. Formerly these birds appear to have been even tamer 

 than at present. Cowley (in the year 1684) says that ' the turtle- 

 doves were so tame that they would often alight upon our hats and 

 arms, so that we could take them alive, they not fearing man until 



