No. 426.] MWEMERTEAN PARASITES OF CRABS. 433 
He also describes the ovarian pouches as opening ventrally, 
and states that their external openings are provided with con- 
tractile lids which serve to close the openings, except when 
the ova are being extruded. Both Dieck and van Beneden 
speak of the minute white specks seen on the bodies of the 
females with ripe ova, while Dieck’s observations on the 
appearance of the egg strings, the eggs themselves and their 
early development, as well as the appearance and peculiarities 
of the embryos, answer equally well for Kolliker’s species ; and, 
finally, his statement that the worms, after having devoured 
the eggs of the crab, find their way to the gills, where they 
live as ectoparasites, is in perfect accord with the observations 
on carcinophila described below, although his interpretation of 
the life history of the worms seems to be in error. 
While it would be unwarranted to say that Dieck’s descrip- 
tions of the anatomy of his Cephalothrix galathee are incorrect 
in so far as they do not agree with the structures found in 
Kolliker's species, yet it would seem most remarkable if 
there were to be found in the same locality two species of 
nemerteans belonging to entirely different orders which agree 
so perfectly in color, size, external appearance ; in possessing 
the same peculiarities in regard to the ocelli, structure of 
body walls, mucous glands, and other features; in baving the 
same peculiar habits due to a parasitic life; in laying eggs 
which have the same appearance and mode of cleavage, and 
which in their development give rise to perfectly similar 
embryos. Likewise remarkable among the nemerteans, 
although it is known in a few forms, is Dieck's observation 
that while most of the eggs are laid before cleavage, yet ferti- 
lization and early cleavage sometimes take place within the 
body of the parent. McIntosh states that this is also true in 
N. carcinophila. It should be noted in this connection that 
Dieck found but a single male, which was 2 cm. in length, 
although the females were abundant and of much larger size, 
some of them being as much as 7 cm. in length. He con- 
sidered it probable that the sperm from a single male entered 
the ovaries of all of the five or six females which might live on 
the same crab. 
