PREJUDICES OF SENSE. 159 



animals under conditions of existence not habitual to 

 the species ; and which, from being casual and inci- 

 dental, may be termed unnatural — that is, contrary 

 to their usual natures. First, as regards the habits 

 of animals ; upon which, as will be hereafter seen, 

 their station in the scale of nature so much depends ; 

 I shall adduce a striking instance, which might have 

 given rise to a prejudice of this sort, in a case 

 witnessed by myself this year. A particular tree 

 on the lawn, immediately opposite my library 

 window, is the usual station of two grey fly- 

 catchers, who have frequented it annually for the 

 last five years. Those who are acquainted with 

 the manners of this bird, know that it habitually 

 lives seated upon trees, where it remains stationary, 

 darting occasionally upon passing insects, and re- 

 turning to the same twig, without perching on the 

 ground. This peculiarity of habit is confirmed by 

 its organisation : for, on looking to the feet of the 

 bird, we see they are of such a construction as to 

 incapacitate it from habitually walking, or even 

 hopping, upon the ground. Nevertheless, I ob- 

 served this year, for the first time, one of these 

 birds in such a situation: it was upon the grass 

 but once ; and then, apparently, to secure an insect 

 w r hich it had wounded, but not captured, in its first 

 assault. Now, had this fact been witnessed by an 

 observer, not acquainted with the ordinary habits 

 of the species, and ignorant of the influence which 

 structure exercises upon habits, he would at once 

 affirm, from his own personal experience, that the 

 grey fly-catcher, and, consequently, all the species of 

 the same genus, were in the habit of frequenting 



