HELIX POMATIA. Dib 
very long and slender flagellum, which is slightly swollen at the end; the short 
PENIS is continuous with the epiphallus, and enters the ArrkrumM by a somewhat 
slender neck. 
The ALIMENTARY SYSTEM has the GiSOPHAGUS 
partially encircled by the whitish and voluminous 
SALIVARY GLANDS, beyond which the short canal 
expands and forms the proventiculus or Crop, 
followed by the true SroMACH, near to whieh are 
the openings of the BILIARY DUCTS from the 
digestive gland or liver; the INTESTINE is of the Fic. BN neal Be oe Ee ea 
ordinary triodromous! character, with the usual RLal Sanglion (eiier Maan Eecaeok 
three distinct flexures or tracts, and terminates we, mouth: #7, nerve ring: 5. radula 
by the respiratory orili-:e. sac; s.d@. salivary duct on the oesophagus. 
The JAW or mandible is strictly odontognathous, four or five millimetres wide 
from side to side, arcnate from front to back, a 
erescentic in shape, and dark brown in colour, rae tes Be 
without any perceptible median beak or rostrum, : ih Rs 
but usually with about six widely separated Ay : 
and distinet vertical and parallel ribs denticu- 
lating both the upper and lower margins, and six 44 
or more subsidiary ridges which extend only Fic.29),— Jaw or mandible of ffe/zx 
partially across the jaw and slightly crenulate — fomatia L., < 10. 
the cutting edge. The whole anterior surface (Preston Candover, Hants., collected 
is beautifully sculptured with fine and delicate DY th Rev: MH. P. Fitzgerald). 
vertical and with sinuous transverse strive parallel with the upper and lower margins. 
The RADULA or odontophore is pale in colour and of the usual elongate form, 
being about ten mill. long and five mill. wide, and usually possessing about 175 
slightly flexuous transverse rows of teeth, each row composed of 159 teeth, and 
constituted by a median series of narrowly tricuspid teeth, of which the mesoconc 
is broad, strong, and powerful, with a comparatively insignificant ectocone at each 
side; the laterals are bifid, with an immense mesocone and a well-defined ectocone, 
SAAR ARAMA GIRY # 
Fic. 291.—Representative denticles from the radula of //elix pomatia I.., highly magnified (from a 
preparation by the Rev. Prof. Gwatkin). 
the endoconic expansion of the mesocone becoming imperceptibly more pronounced 
through a series of transitional teeth and at or about the fiftieth row forms a 
perceptible endoconie cutting point upon the mesocone; the marginals are broad 
and trifid, the mesocone having developed a distinct endoconic cutting point and 
being still the largest, though the difference in size has been greatly reduced. 
The formula of a Swiss specimen prepared by the Rey. Prof. Gwatkin is 
294+ 59 +414 59 4 29 x 175 = 27,825 teeth. 
73 
Q 
The number of longitudinal and transverse rows is, however, in this species 
eminently variable, a very striking ease of this diversity being a Caterham specimen 
reported by Mr. W. Moss, which possessed 225 rows of 181 teeth each or a total of 
40,725 teeth; while Tate gives the formula of the species as 140 rows of 151 teeth 
each, or 21,140 teeth. : 
The development of the odontophore in the embryo shows the usual course of 
evolution,! the teeth originating as a few chitinous amorphous nodules, which in 
succeeding rows increase in number and gradually acquire several sharply pointed 
Fic. 292.—A transverse row of teeth from the radula 
f, / of an early embryonal specimen of //edix fomatia L.; 
highly magnified (after Wiegmann). 
recurved processes or fangs characteristic of the transitional or echinate stage, and 
which gradually give place to the simpler type of teeth present in the adult. 
1 Moncg. i., p. 257, f. 516. 
