A LAND SNAIL 121 
oviduct; the mucous glands, two bunches of tubular glands; and 
the dart-sac, a thick-walled sac which contains a calcareous spicule. 
Identify these organs. 
The vas deferens, after separating from the oviduct, passes 
under the retractor muscles of the tentacle to the distal end of 
the penis. This organ has already been noted; it is tubular in 
shape and lies in a bent position across the wsophagus. A 
retractor muscle inserted at the bend connects it with the dorsal 
body-wall. At the point where the vas deferens meets it is the 
flagellum, a long, tubular sac into which spermatozoa pass from 
the vas deferens and where they are massed together to form 
spermatophores. Both penis and vagina communicate, side by 
side, with the genital cloaca, which opens to the exterior through 
the common genital pore. 
When two animals pair each receives a spermatophore from 
the other. This passes into the receptaculum seminis, which 
is thus filled with the spermatozoa of the other animal, and 
these finally fertilize the eggs as they pass into the vagina from 
the oviduct. 
Exercise 7. Make a semidiagrammatic drawing of the reproduc- 
tive organs on a scale of 2. 
Split the dart-sac and take out the dart; mount it on a 
slide in water or glycerine and examine it under a compound 
microscope. 
Exercise 8. Draw the dart. 
The nervous system. Sever the cesophagus and remove the 
reproductive and digestive systems, leaving the pharynx in 
the body and taking care not to injure any of the nerves. The 
principal ganglia are contained in the nerve collar. The two 
supraesophageal ganglia, which constitute the brain, will be seen 
joined by a broad transverse commissure. From their anterior 
surface nerves run to the tentacles, and from their inner 
