
436 THE AMERICAN NATURALIST:  [Vor. XXXVI. 
Cephalothrix galathee, where he believed that he found the crab's 
blood corpuscles within the intestinal canal of the worms. 
In many of the crabs on which I found only a small number 
of the parasites no injury to the gills was apparent, the ability 
on the part of the crab to repair its injured tissues being 
sufficient to prevent the gills being destroyed. When the 
worms were abundant, however, some of the gill plates were 
blackened, torn, and degenerated. 
A large number of lady crabs obtained from Woods Hole 
and Martha’s Vineyard, Mass., in July and August, 1900, were 
examined, and the parasitic nemerteans found in the gills in 
about one-tenth of the number. When present on one side of 
the body they were almost always found on the other side also. 
I found them only on female crabs, and did not find them in 
the gills when the crabs were carrying eggs. The worms 
cling tenaciously to the gills when these are removed from the 
crab. A gill cut from a crab and placed in a dish of sea water 
is not deserted by its parasites for several days, — or not until 
it decomposes. When forcibly removed from the gills the 
worms live several weeks in sea water, crawling sluggishly 
about, and often collecting in masses with their bodies placed 
lengthwise or folded sharply so that the anterior portion of the 
body lies parallel and in contact with the posterior portion, 
exactly as when living in the gills. Masses of them often col- 
lect on the surface of the water where it comes in contact with 
the sides of the vessel. 
They secrete a very sticky mucous covering and when touched 
with a needle or drawn into a pipette attach themselves to it 
with exasperating tenacity. After living several weeks without 
_ food the worms become much smaller than when first collected. 
. Several dozen spider crabs (Libinia canaliculata), some of 
which carried eggs, a number of blue crabs (Callinectes hasta- 
tus) with eggs, and many rock crabs (Cancer amenus) and green 
crabs (Carcinus manas) without eggs were examined without 
finding any nemerteans. I quite expected to find them on the 
