THE FLATWORM AS AN ENEMY OF FLORIDA OYSTERS. 4 
At Port Inglis and Cedar Keys the destruction during the season 
was estimated to be about 30 per cent. One or two localities, how- 
ever, revealed a mortality as great as 90 per cent, but the excess 
should not be attributed to the turbellarian, since many of the empty 
shells or “‘boxes”’ contained spat which had set before the depreda- 
tions of the worms had occurred, the mortality of these oysters being 
due evidently to other causes. When the devastation was at its 
height the affected oysters, as a rule, contained from 1 to 3 worms, 
although as many as 8 or 10 are said to have been taken from a single 
oyster. During the early part of the season about 100 oysters per 
barrel contained worms, but by February, the time of the examina- 
tion, the trouble had abated to such an extent that not more than 1 
or 2 worms were taken in 20 barrels of stock. It is worthy of remark 
that on the Port Inglis and Cedar Keys bars no small oysters were 
found or reported containing worms, nor did any of the empty shells 
of the small sizes show any malformations indicating that a defensive 
struggle had taken place. 
DESCRIPTION OF THE FLATWORM. 
Although this pest is known to the oyster dealers, planters, and 
shuckers of Florida as the “leech,” it is an animal of very different 
type, belonging to the branch of wormlike animals called platyhel- 
minthes, class turbellaria, and order polycladida.* Since the general 
character and habits of this turbellarian compare closely with the 
similar pest found in New South Wales, and described by Dr. Stead, 
the name “‘wafer”’ would be a more suitable and less misleading one 
for common use. 
The worm is almost flat, more or less circular in outline, and 
measures from about one-half to three-quarters inch in diameter. 
It has occasionally been observed, when feeding, to be so distended 
that it would cover half the body of the oyster. When disturbed it 
usually rolls up into a sort of a tube, the margins then becoming 
curled and very irregular. The upper surface is drab to dark-brown 
in color, sometimes nearly black, and at times finely stippled with 
darker spots; the central portion, posterior to the eyes, is, as a 
general thing, of a lighter aad than the remainder of the surface; 
when taken from an alcoholic solution and allowed to dry, a whitish 
mucus coating is observed. The lower surface is whitish to cream 
color. The worm, when removed from the oyster, is soft and slimy, 
and on very moderate pressure breaks up or runs into a jellylike 
mass, apparently without much structure. When placed in alcohol 
of about 75 per cent strength it becomes firm and somewhat leathery. 
PHYSICAL CONDITIONS. 
The turbellarians were found to thrive in only those localities where 
the salinity of the water remained comparatively high, and not in 
areas where decided changes in density caused by freshets occur at 
certain seasons. The temperature is also an important factor in their 
activity and even their existence. If the water is chilled considerably 
below the normal it may cause their complete disappearance or 
a Harry K. Harring, of the Bureau of Standards and custodian of Rotatoria, U. S. National Museum, is 
engaged in astudy of the turbellarian, which will probably prove to be a representative of a new genus. 
