vii MOLLUSCA 281 



are apt to remain alive in it and to accumulate, if they are numerous in 

 the water. Oysters, Mussels, and other edible Pelecypoda living in 

 waters polluted by drainage containing such disease germs are con- 

 sequently liable to be a source of serious danger to persons eating them 

 in an uncooked condition. If kept in pure sea-water the molluscs soon 

 lose their infectivitv. 



BOOK FOR FURTHER STUDY 

 Sedgwick. A Student's Text-book of Zoology, Vol. I. 



