No. 426.] NEMERTEAN PARASITES OF CRABS. 437 
body, and a portion of them will be found among the gill plates 
after twelve to thirty-six hours, but many more remain clinging 
to the crab’s legs. Their behavior to lady crabs, however, — 
males as well as females, — is quite different, and they quickly 
find their way to the gills. The few rock, spider, and blue crabs 
with which I experimented in this way did not prove attractive 
to the worms, although occasionally one of them would enter the 
gills. Far more of them remained `; 
attached to the basal joints of the 
legs for several days. 
Sexually mature worms may be 
found early in July (and probably 
also in June) on the lady crabs 
carrying eggs. But the crabs with 
eggs are shy or else frequent deeper 
water, so that I did not find them 
nearly so abundant in the localities 
noted as were the males and smaller 
females without eggs. 
All my observations on the p. — Carcinonemertes epialti. Ante- 
spegies seeni to indicate Idt ihe e podm < botret ione vem sa 
worms spend their whole existence matic. »,rhynchodzum; o, ocellus; xv, 
on the crab, for I have found them oreli and other organs of head ; s central 
commissure 

i stylet; őr, brain; dc, dorsal 
I Dru 2 ages of development of brain; d. cesophagus; P, pate 
from the egg to the sexually mature chamber o iet i, intestine; Zn, 
lateral nerve. 
worm. I have not, however, fol- 
lowed their history during the winter months, but suspect 
that this time is occupied as a period of slower growth. 
_ The worms apparently occupy nearly a year in attaining 
sexual maturity, and their life history is briefly as follows: 
Eggs laid in mucous tubes among the egg masses of the crab 
in June and July ; cleavage regular and nearly equal, with the 
formation of free-swimming ciliated blastula which develops 
into a ciliated embryo provided with ventrally placed mouth, a 
pair of ocelli, and an anterior and a posterior flagellum, or tuft 
of much longer, consolidated cilia. The embryo leaves the egg 
membrane in this condition and usually remains in the mucous 
tube or among the egg masses of the host, but may swim freely 
