No. 426.] WEMERTEAN PARASITES OF CRABS. 435 

descriptions. Some of the worms are said to be found on — 
various parts of the crab’s body, being most abundant on the 
abdomen, but the gills are not mentioned. An account of 
this species is given also in the WVarrative of the Cruise of the 
Challenger" (Vol. I, p. 169) and is reproduced in Hubrecht’s 
report on the nemerteans (87). 
A further instance of a nemertean parasitic on Crustacea is 
mentioned by Quoy and Gaimard (33), who describe from 
Amboina a small species, apparently belonging to the genus 
Tetrastemma, under the name of Borlasia quadripunctata. 
They state that although it usually lives in the sea, yet it 
is also found at times living in the barnacle (Anatifa). 
So far as I know, the first observations of a nemertean para- 
site of the crab in this country are those by Prof. J. P. McMur- 
rich, who writes me that he found the worms quite numerous 
among the egg masses attached to the abdominal hairs of a 
“lady crab" (Platyonichus ocellatus) July 6, 1889. These 
worms laid several strings of eggs in the manner characteristic 
of the species. The eggs developed normally, as described by 
van Beneden ('61), McIntosh (73), and Dieck (74). 
I first found this nemertean on the gills of the lady crab at 
North Dennis, Mass., situated on Massachusetts Bay, Aug. 6, 
1898, and have since found it abundantly in other regions 
south of Cape Cod. 
The gills of a single crab often harbor as many as forty to 
sixty of these worms, which are of small size and sexually imma- 
ture when found in this position, becoming full-grown and sexu- 
ally mature only when living among the crab's ova. As found 
on the gills the worms vary in color from pale ocher to salmon, 
depending largely on the coloration of the intestinal canal. 
They are of all sizes up to about 15 mm. in length when 
extended and very slender — almost threadlike. The body is 
of about the same diameter throughout and is often folded once 
or twice on itself as it lies between the gill plates of the crab, 
imbedded in considerable mucus. The crab's gills are some- 
times undoubtedly injured by the abundance of the worms, so 
that I am almost sure that the latter feed upon the blood in the 
gills. This was also Dieck’s conclusion in regard to his 
