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species. We take the opportunity of acknow- 
ledging our obligation to those gentlemen. 
" Dear Sir— I am much ashamed that I 
have not answered your letter sooner, but the 
question which Mr. Hunt has put to me re- 
specting the eyes of the Owls, is one which 
I have found some difficulty in answering. 
The eye of that bird is so extremely black, 
and being placed deep in the socket, without 
any white surrounding It, it requires, as you 
say, frequent and attentive examination to 
ascertain the fact. I have paid some atten- 
tion to it, and without any experiment it ap- 
peared to me perfectly immovable ; and di- 
rected to any object only by the motion of the 
head and neck. I mentioned the circum- 
stance to Dr. , who proposed the follow- 
ing experiment, which he said would not be 
likely to produce pain to the bird, and which 
would show more satisfactorily if any motion 
did take place. He formed a white sub- 
stance, about the consistency of paste, a very 
small drop <©f which he fixed upon the eye, 
holding at the same time the eye-lid, and the 
nictitating membrane, so as to prevent its 
passing over the eye. In this state the eye 
