SPECIAL ANATOMY. 223 
duct is short, gradually increases in breadth, and is spi- 
rally twisted. From the duct, as previously mentioned, 
passes a small offset to the vas deferens. The common 
duct of the bladder and oviduct, or vagina, is cylindri- 
cal, and, just before terminating, is joined by a short, 
wide tube, derived from a large, oval sac, which is filled 
with a delicate, reticulated substance. This sac is pecu- 
liar to Vaginulus; its use is problematical. 
The position of the female orifice of generation has 
been already stated. 
Helix. The testicle, very unlike that of slugs, is 
imbedded or commingled with the parenchyma of the 
posterior or superior lobe of the liver ; and, instead of 
having an aciniform appearance, it is composed of fasci- 
culi of short cceca. It is usually of a lighter color than 
the liver. The epididymis is long, and generally very 
much convoluted, and contains a white, silky, tenacious, 
substance, often distending the tube to a considerable 
o, composed of spermatozoa. At its junction with 
the prostate gland, it always receives the duct of a small 
accessory gland, composed, in different species of Helix, 
of from three to nine acini. 
The prostate gland is generally larger than in the 
Limaces ; in H. exoleta it is unusually large. 
The vas deferens generally corresponds in length with 
the curve passing from the termination of the prostate 
gland downwards to the cloaca, and thence to the sum- 
mit of the penis. In H. exoleta and M. albolabris it is 
