172 
ANODONTA — ALIME^JTARY SYSTEM. 
(leticient of prehensile or masticatory organs and leads directly upwards 
hy a short and distensible msophagns to the irregnlarly oval stomach, 
which lies in front of the pericardinm and with the msophagus is im- 
bedded within the digestive gland ; the stomach has thin walls with a 
cadncons, cuticular lining, the Jhrhe trkuspide, which overlays and 
protects the secretory cellnles : there is also a i)yloric cmcal diverticnlnm 
opening on the right side which can be closed up, and contains a 
gelatinous and transparent rod-like body, the Crystalline Style, a 
freely projecting extension or prolongation of this cuticular stomachal 
investment which is most distinctly developed in spring. 
'I'he Digestive tract is convoluted within the visceral sac, especially 
amongst the lobes of the enormous genital glands and in the tissues 
above the foot; it originates from the ventral wall of the stomach, 
passing slightly to the left side during its downward and somewhat 
backward course, it then curves upwards somewhat parallel to the 
l)osteri(n' margin, and cm ai)proaching the pericardium bends abruptly 
I’ lO. 339 . — Anodonta Q'ifWt’ri dissected to show the arrangement and convolutions of the alimen- 
tary system; the right pallial lobe, branchitT; and palps have been removed and the alimentary 
canal, ventricle of the heart and nephridium opened up to show their internal structure (after Howes). 
rtr. auricle of the heart ; a. ad. anterior adductor ; a.s. anal siphon ; hr. branchiae ; hr.s. branchial 
siphon ; d.o. dorsal orifice ; /. foot ; genital gland ; g.o. genital orifice ; ib.c. infra-branchial 
chamber; /. fiver or digestive gland, with bile ducts opened up; ni. mouth; cc. oesophagus ; 
p.ad. posterior adductor ; pc. pericardial chamber, showing the left reno-pericardial orifice near 
the anterior end ; r. rectum ; r.o. renal organ or organ of liojanus st. stomach ; ty. typhlosole 
of rectum ; w. ureter ; v. ventricle of heart, 
backward upon itself, returning to the base of the foot on a course 
parallel to Imt outside the first upw'ard tract, it again becomes ahrui)tly 
bent u})wards, traversing the body in a backward direction and on the 
right side of the body, gradually bending forward as the final tract 
or rectum towards the antero-ventral region of the pericardium, 
which it penetrates, passing through the ventricle and emerging 
from the jjostero-dorsal surface of the pericardium, afterwards run- 
