562 



LECTURE Xxn. 



207 



Helix pomatia, dissected. 



from the duct in Helix pomatia, and a very long one in Helix arbus- 

 torum: the duct is short and simple in the slug (^Limax). The 

 genital vestibule receives the terminal outlets of two groups of 

 branched caeca (x, x), or " multifid vesicles," the function of which is 

 unknown. But the complexity of the generative apparatus does not 

 end here : the snail is provided with a pyriform muscular sac {y), the 

 aperture of which terminates close to the generative outlet. The 

 expanded base or head of a slender conical calcareous style or dart 

 (6, in the detached figure) is attached to the fundus of the sac (a) . 

 its sharp apex (c) extends close to the orifice, and by the contraction 

 of the sac it can be proti-uded outwards. With it the snails pierce 

 each other's skin, and the function of this curious organ would seem 

 to be to cause a preliminary excitement to the reciprocal union of the 

 two androgynous individuals. 



