INTESTINAL WORMS. 169 
joint, yet nearer the anterior edge, with two openings: through the 
anterior and larger the penis is evolved; the posterior smaller 
is the female sexual opening: round both of them are minute 
white points which Escuricur! concluded, under high powers of 
the microscope, to be follicles (mucous crypts of the skin). The 
eges of Lothriocephalus have a hard shell, as in the Déistomes, of a 
brown or brownish-yellow colour, and seem like them to spring 
open with a sort of hood. In the thorn-headed and round-worms 
the sexes are distinct, and may be often recognised externally 
by their different form and size. In the thorn-headed worms the 
sexual organs fill the greater part of the cavity of the body. From 
the sheath that surrounds the proboscis there runs backward in the 
axis of the body a band-like structure, which has been erroneously 
supposed to be a canal, but which is for the support of the organs 
that prepare the germ or the seed (ligamentum suspensorium) ; VON 
SIEBOLD supposes that even the ovaries are developed in this organ. 
These ovaries are found free in the abdominal cavity, as masses of 
oblong-round eggs: the eggs become detached as they advance in 
development. The muscular oviduct terminates in a very small 
opening, scarcely visible at-the posterior part of the body: it has at 
its anterior extremity an infundibular expansion which alternately 
widens and contracts, and takes up the eggs that were floating freely 
in the cavity of the body and moves them onwards’ to the oviduct. 
This arrangement, in virtue of which the oviduct opens freely into 
the cavity of the abdomen and is not an immediate continuation of 
the ovary, is found in most vertebrates, with the exception of the 
osseous Fishes, but has not hitherto been observed in invertebrates 
except in Echinorhynchus. In male thorn-headed worms there are 
usually two testes lying one behind the other. The penis lies in a 
sac having a conical appendage that can be everted from the body 
in the form of a little bell. 
Amongst the Thread-worms the males are less frequent than the 
females: they are smaller and more slender, and may frequently be 
1 See Escuricut Anatomisch-physiologische Untersuchungen weber die Bothrio- 
cephalen; Act. Acad. Ces. Leop. Carol. Nat. Curios. Vol. X1x. Supplem. 1. 1840. 
2 Von SreEBOLD in Burpacn’s Physiologie, 11. s. 197. See a figure in Burow 
Echinorhynchi strumosi Anatome. Diss. Zootom. Regiomonti, 1836, 8vo. fig. 1g. fig. 6 ; 
comp. DUJARDIN op. cit. p. 494, Pl. vu. fig. 7, D5. (Zchinorhynchus anthuris, a species 
from the freshwater Salamander). 
