194 ZOOLOGY 
water, which enters the pallial chamber by the ventral 
siphon. 
The nephridia of Lamellibranchs are usually known as 
the Organs of Bojanus. There is a single pair, and each con- 
sists of a glandular or secretory portion which has an opening 
' t ' ‘\ 
4116 46) 11 19 
Fic. 117.—Diagrams of a Schematic Mollusc. After Lankester—Zoological Articles 
reprinted from the Encyclopedia Britannica. 
A. Dorsal view, showing the heart, 9. Internal opening of nephridium. 
pericardium, generative organs, 10. External opening of nephridium. 
and nephridia. 11. Opening of genital gland. 
B. Ventral view, showing the nervous 12. Cerebral ganglion. 
system. 13. Pleural ganglion. 
C. Lateral view. 14. Pedal ganglion. 
1. Mouth. 15. Visceral ganglion. 
2. Nerve ring. 16. Foot. 
3. Oesophagus. 17. Anterior aorta. 
4. Liver. 18. Gill. 
5. Anus. 19. Tentacle. 
6. Pericardium. 20. Auditory vesicle. 
7. Heart. Ventricle. 21. Olfactory ganglion, 
8 in A. Auricle. 22. Abdominal ganglion developed on 
8 in C. Wall of pericardium. the visceral loop. 
into the pericardium, and of a ureter which opens to the exterior 
in the neighbourhood of the orifice of the generative glands. In 
the oyster the kidney is much less compact, and its secretory 
part is scattered through the body, even reaching the mantle. 
