122 



SENSES 



particular function to any of them, except it he to tlie sensory 



hairs. These are seated on various 

 parts of the body. The chitinous 

 covering, being a dead, hard substance, 

 has no nerves distributed in it, but it 

 is pierced with orifices, and in some of 

 these there is implanted a hair which 

 at its base is in connexion with a 

 nerve ; such a structure may pos- 

 sibly be sensitive not only to contact 

 %gMSW^'^-?j!i^igg^:, n. with solid bodies, but even to vari- 



_ ^, - ., ,. , ,. r ous kinds of vibration. We give a 



Fig. 67. — ijongitudmal section oi ° 



portion ot caudal appendage of figure (Fig. 67) of some of these hairs 

 ^. ^X^;^^^ on the caudal appendage of a cricket, 



dermis ; n, nerve ; h}, integu- after Voill Eath, The Small hairS Oil 

 mental hairs, not sensitive ; Jr. ,■, , p p ,^ -i •,■ • ,i ■ 



ordinary hair; A^ sensory hair ; ^^e OUter Surface of the chltni m thlS 



h*, "bladder-like hair ; .% sense- figure have no sensory function, but 

 each of the others probably has ; and 

 these latter, being each accompanied by a different structure, 

 must, though so closely approximated, 

 be supposed to have a different function ; 

 but in what way those that have no 

 direct connexion with a nerve may act 

 it is difficult to guess. 



The antennae of Insects are the seats 

 of a great variety of sense organs, many 

 of which are modifications of the hair, 

 pit and nerve structure we have described 

 above, but others cannot be Isrought 

 within this category. Amongst these 

 we may mention the pits covered with 

 membrane (figured l;iy various writers), 

 perforations of the chitin without any 

 hair, and membranous bodies either con- 

 cealed in cavities or partially protruding 

 therefrom. 



Various parts of the mouth are also 

 the seats of sense organs of diiTerent kinds, some of them of a 

 compound character ; in such cases there may be a considerable 

 number of hairs seated on branches of a common nerve as figured 



sck 



-Longitudinal section 

 of apex of palpus of Pieris 

 hrassicae : sch, scales ; ch, 

 chitin ; hyp, hypodermis ; 

 n, nerve ; sz, sense cells ; 

 sh, sense hairs. (After 

 Tom Kath. ) 



