THE NEMERTEAN PARASITES OF CRABS. 
"WESLEY KR. COE. 
YALE UNIVERSITY. 
In 1844 Kolliker found a small species of nemertean among 
the egg masses carried about on the abdominal hairs of a ** small 
crab" at Messina. This worm he named Nemertes carcino- 
philos! and gave a fairly good description of its anatomy (45). 
Fifteen years later van Beneden found a similar species among 
the eggs of the green crab (Carcinus manas) on the coast of 
Belgium and, having overlooked Kólliker's descriptions, rede- 
scribed and figured it as Polia involuta (61). The worms were 
said to be small, slender, yellowish or rosy in color, with two 
ocelli and a very short proboscis, armed with central stylet only. 
They lived in delicate mucous sheaths among the crab's ova, 
and often two individuals — a male and a female — lay side by 
side, or with their bodies somewhat folded, in the same tube. 
Van Beneden decided that the worm was not a true parasite, 
but rather that it merely occupied the egg masses of the crab 
as convenient places for building its tube and depositing its 
ova, as well as a place well protected and furnished with food. 
The females were 2—3 cm. in length, although the males meas- 
ured scarcely 1 cm. Some of the younger individuals were 
only 2 mm. long. There are figures showing the form and 
color of the living worms, several of anatomical details, of 
the eggs in various stages of development, and of the early 
embryos before and after the molting of the larval skin. 
These figures are generally accurate, as is also the interesting 
account of the development. The large nerves passing forward 
from the dorsal ganglia are described as excretory canals open- 
ing on the lateral margins of the head, although the author 
states that they seem to be a continuation of the ganglia. The 
1 Spelled cartinophilos. 
431 
