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XX. Memoir upon the compound and smooth or simple Eyes of 

 Insects, uvd on the Manner in ivhich these lioo Species of 

 Eyes concur in Vision. By M. Marcel de Serres, Hro~ 

 Jessor oj the Sciences in the Imperial University*. 



Visus i^itur quo insect, i szaiident nulla [leiiitus ratione cum nostris oculis 

 aiit cum Ciimfia ohscura i.i qua iiium species, reflexiojiis ope, simper 

 charta auC panno albiciinte Duiiiuuiiiur in ronipniationeni vcn're potest. 

 SWAMMKUO.^M, BibilaNiitura, torn. ). p. 50-2. 



oiGFJT seems to be one of the most perfect of the senses of 

 insects ; and in this respect these animals are in the first Hne 

 aniong those witliout vertebrfe as birds are among- those with 

 vertebraj. Both enjoy a very lonj^ sight ; and we know tit how 

 great a distance the maggot, hke the bird of prey, perceives 

 the object wiiich it wishes to devour. Is tJie great tjuantity of 

 air inhaknl by tliese two orders of animals in the act of resjiira- 

 tion, tlie cause of the acuteness of this sense, as it is of their 

 muscular strength? or must we account for it from tine great 

 development of tlioir retina and the largeness of their eyes ? 

 However difficult it may be to resolve a question abounding so 

 much with difficuUy, it is jjrobable that insects and birds owe 

 equally to the great abundance of air v/hich thev inhale, the acute- 

 ness of their senses, and the activity of their digestion ; finallv, 

 the violence of their passion-;, it we may so express ourselves. " 



Far different from the vertebral aiiimals in the .structure of 

 their eyes, insects enjoy the impisssion of external objects by 

 means peculiar to themselves, and which furnish proofs that na- 

 ture knows how to attain the same end by very opposite vi'ays- 

 In fact, the operation of vision is not performed by insects in 

 the same way as with most animals by the action of the lu- 

 minous r:tys, which, after passing tinongh the ptipil, collect on 

 the retina, but rather l)y the shaking of the optic nerves occa- 

 fcioned by the light wliich passes thiongh the cornea. These 

 eyes are constructed so as to receive the im.-iges of oljjects by 

 t!;e simple shock of the rays which tlsese objects rellect, nnd this 

 method of feeling must necessarily l)e very acute. Besides, in- 

 sects not having, like the vertebral animals, pupils susceptible of 

 contracting, it would seem that vision ought to be very perfect 

 with them, on account of tlie great number of rays which fall 

 continually on the fiicets of their eyes. 



Nevertheless, one of the great inconveniences win'ch re- 

 sults from the org:i!ii.-;ation of insects, is the kind of im- 

 movcability of the parts in which tlieii eyes an^ fixed. But 

 nature has re.nedied whatever is imfavouiablc in this orga- 

 nization, bv rendering the evps of insects very much com- 

 plicated, and by multiplying ihp'r facets in such a way that one 



* Ma^uSiit K*tryloi)iJiqw, Feb. 18:4. 



and 



