REFLEXES, INSTINCT, AND REASON 429 



of otlier tlian mechaniciil behavior amon^ aniiiKils to great 

 lengtlis. Loel) introduce.s a pajxT written in isiuj on instinct 

 and will in animals as follows: 



*'In the biolo«:;i('al literature one still fiiuls authors wlio treat the 

 ' instinct ' or the ' will ' of animals as a circumstance wliich (let<Tniines 

 motions, so that the scientist who enters the region of animated nature 

 encounters an entirely new category of causes, such as are said contin- 

 ually to produce before our eyes great effects, without it Ix'ing possible 

 for an engineer ever to make use of these causes in the jthysi<Hl world. 

 ' Instinct' and ' will' in animals, as causes whicli determine movements, 

 stand upon the same j^lane as the suj)ernatural jjowers of theologians, 

 which are also said to determine motions, but uj)on which an engineer 

 could not well rely. 



"My investigations on the heii()lro!)ism of animals IcmI me to 

 analyze in a few cases the conditions which determine the ai>parently 

 accidental direction of animal movements which, according to tradi- 

 tional notions, are called voluntary or instinctive. Wherever I have 

 thus far investigated the cause of such 'voluntary' or 'instinctive' 

 movements in animals, I have without excei)tion discovered such 

 circumstances at work as are known in inanimate nature as determi- 

 nate movements. By the help of these causes it is possible to control 

 the 'voluntary' movements of a living animal just as securely and 

 unequivocally as the engineer has been able to control the movenient.s 

 in inanimate nature. What has been taken for the effect of 'will' or 

 'instinct' is in reality the effect of light, of gravity, of friction, of 

 chemical forces, etc." 



But Jennings, a ver}^ careful and industrious student of the 

 behavior of the protozoa, whose studies have been j)erhaps more 

 detailed and prolonged than those of any other investigator cf 

 the same subject, closes a fascinating volume on his work wi. . 

 the following jiaragraph: 



"The present paper may be considered as the summ.ng up of the 

 general resuhs of several years' work by the author on the Ix'havior of 

 the lowest organisms. This work has shown that in thes<' creatures the 

 behavior is not as a rule on the troi»ism plan— a set, force<l metluxi of 

 reacting to each i)articular agent— but takes place in a nuich more 

 flexil)le, less directly machinelike way, by the method of trial and 

 error. This method involves many of the fundamental «|uaHlie8 



