SPECIAL ANATOMY. 207 
teeth preserve the same form in the lines from hefore 
backwards ; the central line always differs from the 
others, and the teeth also vary gradually in form and 
size as they pass off from the central line laterally. They 
also vary slightly in form in different species. This 
lamina protrudes from the buccal body posteriorly, into 
a short, rounded, protuberant, blind sac, within which it 
appears to undergo a constant growth, as it is worn away 
by attrition anteriorly ; for its use appears not only to 
facilitate the passage of the food onwards to the oesoph- 
agus, but also to act as a sort of rasp for triturating it, by 
means of the powerful muscles composing the buccal body. 
Into the posterior, inferior part of the buccal body, below 
the blind sac of the lingual lamina, is inserted, in a trans- 
verse, curved line, its retractor muscle. This muscle has 
its origin, in common with the retractors of the tentacles, 
from the muscular investment of the visceral cavity, pos- 
terior to the pulmonary cavity, and to the right of the 
rectum. 
The oesophagus proceeds from the upper, posterior part 
of the buccal body backward to the stomach. It is short, 
and dilates gradually into the latter. 
The stomach is a capacious, membranous receptacle, 
when extended being two-thirds the length of the animal. 
In L. variegata and L. agrcstis. anteriorly it is dilated, 
and elongated-oval in form, posteriorly it is intestiniform. 
In L. eampestris, it is nearly uniformly cylindrical 
throughout. Where the stomach terminates in the small 
intestine, it makes a turn forward with the latter, pro- 
