M. Van Beneden on a new genus of Cestoid Worm. 45 
larger at the base, where it is covered with asperities, and when 
unrolled nearly equals the body in length. 
The lemniscus is also lodged in a sac resembling the sheath of 
the tube of Tetrarhynchus, and unrolls itself like that tube. A 
very perceptible retractor muscle arises from the bottom of the 
sheath, and thence extends to the extremity of the lemniscus. 
We agree with Siebold, that, like as in the Trematoda, the 
Nematoidea and other worms, there exists one organ for the for- 
mation of the germ, and another for that of the vitellus. The 
germigenitor (germigéne) occupies almost the whole length of 
one side of the body, having a coiled form, and 1s easily detected 
when containing germs. 
The yitellogenitor (vzte/logéne) is made up of cells more or less 
round, often very clear, and which are distributed throughout 
the parenchyma in large number. Ova im their interior are often 
to be seen in course of development. We believe that the cells 
rupture, scattermg the vitelline globules in the cavity of the 
body, which then envelope the germinal vesicles after they have 
undergone contact with the spermatozoa. 
A dull white organ is also seen in the centre of the body, 
which, when the animal is compressed, appears a tortuous cord, 
like the testes of insects. It has distinct walls, and may be com- 
pletely uncoiled. We have supposed this tube might terminate 
at the base of the lemniscus, but have been unable to determine 
this opinion by observation. We regard this organ as the testes, 
but do not think it discharges its product externally. 
In the interior of the body we have observed ova in course of 
development, having experienced the action of the spermatozoa; 
but as there is no perceptible opening externally, we are compelled 
to admit fecundation to result from the spermatozoa of the same 
animal, which implies complete hermaphrodism. 
Helminthologists generally admit the existence of natural 
vents for the escape of the reproductive products, but, in the 
worm described, nothing of the sort is seen. When the skin of 
an animal, on the object-glass of the microscope, ruptures, the 
ova escape through the rent. 
The ova are very small, measuring but >35th of a millimetre, 
but are not otherwise remarkable. It is worth while to observe, 
however, the great difference in size the ova present in animals 
closely allied. Thus in Bothriocephalus flos the ova at the time of 
their discharge have eight or nine times the volume, and admit 
of the ready observation of their cells in process of organization. 
Affinities —The Echinobothriumis allied to the Bothriocephale, 
but cannot be included in that or any established genus. In 
seeking to classify this worm we have been struck with the sin- 
