ORIGIN OF SOME GENERAL ERRORS. 819 



dity is such that a celebrated botanist has said of it that " if a 

 single plant were uninterrupted in its possible increase for twenty 

 years, within that time it would cover an extent equal to the 

 entire surface of the globe." 



Our botanizing excursion, so successful, so full of interest, and 

 so much enjoyed, having concluded, we bade adieu to matchless 

 Killarney, and will not soon have effaced from our memories " the 

 home of the ferns/' 



■»»» 



ORIGIN OF SOME GENERAL ERRORS.* 



Br Hebb S. EXNEE. 



TTTHILE we endeavor to distinguish between instinct and rea- 

 V V son, we are accustomed to speak of such skill and conform- 

 ity of actions to a given end as are exhibited by birds in building 

 their nests, or by societies of insects, as more resembling what we 

 call reason. We may mark the difference, however, by observing 

 that instinct develops its qualities only within a limited sphere 

 and in view of a limited end. Birds can weave filaments into 

 nests, attach them to branches, and adapt the forms of their work 

 to those of the tree and its limbs ; but their talents in weaving 

 are of no use in helping them release themselves when caught in 

 a snare, and they will then struggle as wildly and vainly as an 

 animal that never built a nest. A hen will lay an egg every day 

 in the same place till the quota is completed, and will then sit 

 upon them ; but many hens will sit all the same, and for the full 

 time, if the eggs are taken away as they are laid. These ex- 

 amples illustrate how instinctive processes are produced simply 

 as determined combinations — or work only in view of a special 

 end. The actions provoked by them will remain the same, even 

 when they have become purposeless. On the other hand, the as- 

 sociations of the processes can not be broken, and the skill which 

 the bird directs to building her nest is not capable of being em- 

 ployed for any other end. 



The more developed the instinct, the more stable are the com- 

 binations of phenomena and nervous conditions under which it 

 works ; the weaker the combinations, the more nearly the animal's 

 mode of action approaches what we call reason. We should judge 

 of the intelligence of an animal, not by single acts surprising to 

 human understanding, but according to the diversity of the situa- 

 tions in which that animal can use its faculties. The weakness of 

 reason in the animal always has the same character, and lies in the 

 impossibility or difficulty of breaking certain associations and the 

 incapacity to produce out of two combinations, by transferring a 



* From a communication to the Sixty-first Congress of German Naturalists and Physicians. 



