THE FLATWORM AS AN ENEMY OF FLORIDA OYSTERS. 7 
end or hinge. By carefully opening an infested oyster and removing 
the right valve, the worm may be observed as a thin sheet, closely 
adherent to the meat, and more or less covered with a slimy mucus. 
(See fig. 3.) It was stated by the oyster dealer, who was interested 
in this subject, that he had found the worms in about the same rela- 
tive position mentioned above, but on the reverse side or between 
the meat and lower valve, so that it was necessary after taking off 
the upper valve to turn the oyster over in order to see the worm. 
It was not determined how long the oyster can successfully with- 
stand an attack or whether it is able to recover after an invasion. 
It is the opinion of some dealers that the oysters are killed within 
two or three days, but this is evidently too brief a period, at least for 
the majority of cases. An examination of many of the oysters showed 
plainly, both in the meats and shells, that a hard, continuous, and 
defensive struggle for existence had taken place. The oysters, which 
were alive when opened, were poor, watery, and shriveled, to a degree 
depending upon the duration of the plague. Being robbed of its 
juices and its vitality probably reduced by secretions of the worm, 
starvation and death would ultimately follow. Up to this time no 
odor of decomposition was observed. 
When carefully examined, the meat and shell often reveal the 
successive stages of the battle between the feasting turbellarian 
and the helpless oyster. With a slow but continued Joss of its life 
juices and consequently contracting meat, the mantle gradually 
withdraws from the margins, particularly along the ventral side, and 
leaves a dark or blackened border or band of shell substance. (See 
fig. 4.) As the struggle continues, a thin ridgelike deposit of the 
shell substance may form along the gill side about one-half inch from 
the edge of the shell, and extend from the hinge to the tips. (See 
fig. 5.) At times asecond or inner ridgeis secreted. (See fig. 6.) The 
oyster, now being reduced to a smaller space by additional loss of its 
juices, has thus accommodated itself to a still smaller shell cavity. 
These ridges are doubtless a mechanical consequence of the shrinkage 
of the oyster; they indicate that the attack is persisted in and that 
considerable time elapses before death ensues. ‘The ridges and other 
deposits are composed of regular shell material—calcium carbonate, 
and conchiolin; nacreous and crystalline layers are both present. 
(See figs. 7 and 8.) 
CONCLUSIONS AND RECOMMENDATIONS. 
1. Although oysters may be able to resist a brief invasion of the 
turbellarian, it does not appear that they possess the means to ward 
off an assault in harassing numbers, if long continued. 
2. After the turbellarian has once gained admission within the 
oyster, there appears to be no method of combating the enemy. The 
eye ridges deposited by the oyster afford only a temporary 
relief. 
_ 3. It is recommended that a careful working or cultivation of the 
- beds in the infested district be carried on systematically, and that 
new, air-dried cultch and fresh seed stock be used when possible. 
All marine grasses and other objects under which the turbellarian 

a Mr. Williams, Cedar Keys, Fla. 
