562 



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 (a;, 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 (i/), the 

 aperture of which terminates close to the generative outlet. The 

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

 {b, 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 protruded 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. 



