LIFE-HISTORY OF BUCEPHALUS HAIMEANOS. 681 
No living cercarie were found in any of the dead oysters 
which I was able to obtain. 
At the end of three days all of the remaining oysters were 
opened. None were found to be infected. 
During July and August heavy rains in the country had 
flooded the marshes, and the water in Newport River had 
become extremely fresh, furnishing conditions which were 
trying to even the healthy oyster. 
The above observations seem to show that the presence of 
the cercariz seems to render the oyster less capable of with- 
standing adverse conditions. While conditions that are 
conducive to the well being of the oyster prevail, the 
presence of the cercariz does not seem to cause any great 
mortality, but, when circumstances arise during which the 
latent vitality of the oyster is called forth, the infected 
oysters are unable to meet the requirements. 
Hven during the best of conditions the parasite must be 
considered as injurious, since it prevents the formation of the 
sexual products. 
From my observations I feel reasonably certain that the 
cercariz thrive best in slightly brackish water, such as 
usually prevails in Newport River. 
It will be noted that similar conditions prevail in the 
localities mentioned above as reporting infected oysters. 
The oysters from the salt water at Fort Macon are without 
the parasite. 
In oysters from the Mullet Pond on Shackelford Bank the 
growth of the cercariz in the oysters which I examined seems 
to have been inhibited. 
It is interesting to note that the water of this pond, by 
reason of its location, is subject to considerable variations in 
salinity. It is normally fed by fresh-water springs, but 
during an extremely high tide or during storms salt water 
may be swept into the pond. 
It is my belief that, during a period when the water was 
somewhat fresh, the cercariz obtained a foothold. Later, 
when by reason of the incoming of salt water and subsequent 
