284 



NOTE ON A DART FOUND IN THE BODY-CAVITY OF HELIX 



ASPERSA. 



By R. G. Baekes, 



Mead 10th March, 1905. 



Among the mollusca there are various calcareous or crystalline 

 secretions, and these secretions may be used for diverse objects. 

 There is found among some bivalves and a few Gastropods a crystalline 

 style. As is well known, this lies in a blind sac, adjoining the 

 intestine, and is probably used as an accessory digestive organ, though 

 only present at certain seasons of the year. It has been observed also 

 to vary in size with the amount of food ingested by the mollusc, 

 suggesting that the structure may represent a reserve of food material 

 with a special secretion, but a chemical modification of sui'plus food. 



Different from both these organs, we find in certain Gastropods, 

 especially the Helicidae, an ergasidium, the special function of which 

 is to stimulate sexual activity. These excitatory functions are not 

 restricted to male or female, and it has even been thought that most 

 molluscs are provided with some special excitatory, or else alluring, 

 organ. Among some Gastropods, as Agriolimax and Zua, there is 

 a special stimulatory organ which is a fleshy, linguiform, eversible 

 process. This organ is either in the genital passage, near the outlet, 

 or in a cleft at the base of the copulatory organs. Usually also 

 this belongs to the masculine apparatus, though in Amalia it is in the 

 feminine parts. 



