of Gasteropodous MoUusca. 411 



a brownish yellow colour. It lies a little behind the buccal mass, 

 near the median line of the body. From its right side issues a 

 small duct {r), which, turning backwards, communicates with the 

 bulb (p), or dilated portion of the copulatory passage, at the 

 point where it receives the tube of the penis. From thence the 

 copulatory passage or channel (o) leads backwards, and for a 

 short way runs parallel to the duct of the testis, to which it is 

 closely adherent ; it soon contracts and turns to the right side. 

 At the point where the contraction takes place it communicates 

 at / with the duct of the testis ; afterwards the walls of the chan- 

 nel continue parallel until it approaches the external orifice, when 

 it suddenly expands into a sort of shallow pouch (w). During 

 copulation, the intromittent organ, entering at this orifice, will 

 pass along the channel just described, probably as far as the bulb, 

 or dilated portion, in connexion with the short duct of the sper- 

 matheca ; from thence the seminal fluid will readily reach that 

 vesicle, to be there retained until required for the fertilization of 

 the ova. How this takes place will be seen if we trace the eggs 

 from the ovary to the external outlet. 



The eggs pass from the ovigerous sacs by the small ducts be- 

 fore described, and, reaching the central duct, find their way at 

 once into the dilated portion (z) of the common oviduct; and 

 there, probably, are advanced another step towards matm'ity : 

 they then pass along the constricted part of the oviduct, and 

 reach the tube of the penis near its junction with the bulb of the 

 copulatory passage, when they will be within the influence of the 

 fluid stored up in the spermatheca, and also of that of the testis 

 of the same individual. The bulb {p), or dilated portion of the 

 channel leading to the spermatheca, may be probably' a sort of 

 reservoir for the retention of the fertilizing fluid secreted by the 

 testis of the same individual. If so, this fluid may be supposed 

 to pass from the duct of the testis at the point (/) where it com- 

 municates with the swelled portion of the channel, and it may 

 be here- that the eggs are fertihzed. During coitus the seminal 

 fluid will pass directly onwards through the duct of the testis to 

 the tube of the penis. And thus, perhaps, we arrive at a correct 

 understanding of the function of those two points of union. The 

 eggs, after being thus fertilized, pass downwards into the chan- 

 nel of the great mucous gland {k), and then become enveloped in 

 their final covering previous to expulsion through the opening 

 (/) at the base of the penis. 



It would appear, from the diagram of Chalidis ccei-ulea given 

 by M. de Quatrefages, that he has confovmded the ovary with 

 the testicle, and that which is called the testicle is probably a 

 portion of the great mucous gland. The salivary gland has the 



