INSTINCT AND EEASON. 133 



in the course of time, investigation may furnish evidence 

 that not a few of them were, or must have been, at one time 

 acquired ; but I very much doubt whether proof will ever be 

 furnished that all classes of instincts in man and other ani- 

 nials for what are instincts in other animals must be equally 

 so in man were acquired. 



Whether or not, however, we are to regard certain in- 

 stincts as part and parcel of the original constitution of the 

 genus, species, or individual, and certain others as acquired 

 either by the individual or his ancestry, there are undoubted 

 attributes of instinct that deserve or demand here a little 

 special attention. These attributes include, for instance 



1. The variability of instinct. 



2. The loss of old instincts, and the 



3. Acquisition of new ones. 



4. Their perversions or derangements. 



5. Their latency. 



6. Their vicariousness. 



7. The dominance of certain of them, and 



8. The antagonism of others. 



The variations of. instinct are illustrated in other chapters 

 for instance, those on 'Adaptiveness,' 'Education,' ' Errors' 

 but, even though there should be some unavoidable recapitula- 

 tion, a few remarks on the subject are here desirable. Some 

 of the best illustrations of the modification of instinct, with, 

 by, or according to circumstances, are to be found in the 

 phenomena of nidification in birds. Nest-building is popularly 

 supposed to be conducted on the same uniform plan, under all 

 circumstances, by the different individuals of the same species; 

 but this is very far from being the case. The variation of 

 instinct in the nidification of birds was long ago shown by 

 Audubon; and recently the late Dr. Pouchet, of Rouen, pointed 

 out the effect of change in the domestic architecture of man 

 on the nest-building operations of the swallow. Adams 

 refers to change of habits as to nidification in the cliff 

 swallow of North America, which is now also taking advan- 

 tage of man's dwellings. Town birds very commonly build 

 differently from country birds of the same species, selecting 

 a different site, shape, or materials, or all their methods 



