464 THOS. H. MONTGOMERY jr., 
e. g. in the arrangement of the musculature, nor yet any signs of 
setal sacks. The only ciliation in Paragordius is found in the ovi- 
ducts: the Nematoda have no ciliation, the Annelida are usually 
richly ciliated. The spermatozoa are elongate and hair-shaped, not 
amoeboid as in the Nematoda. 
Summary. With the Nematoda the Gordiacea have in 
common only one important structure, the tubular genitalia and their 
opening into the cloaca. With the Annelida they agree in the 
structure and innervation of the musculature, and in having dorso- 
ventral mesenteries which divide body cavities bounded by cell layers. 
But there is good reason for doubting the homologies of these mesen- 
teries and body cavities in these two groups of animals. They differ 
from the Annelida in showing no trace at all of true metamerism 
(either in the nervous system, the body cavities, the genitalia or the 
body wall); in the absence of a cerebral ganglion, of a vascular 
system, of setal sacks or extremities; and very markedly in the 
structure. of the genitalia. In view of these facts the Gordiacea 
cannot be regarded as even highly degenerate Annelida, as VEJ- 
DOVSKŸ has done, nor yet as modified Nematoda, the view of 
most of the writers, but must rather be considered a group of 
isolated position, as GRENACHER, VON SIEBOLD and VILLOT have 
regarded them. 
The group of the Gordiacea contains three well defined genera: 
Gordius, Paragordius and Chordodes; until the structure of Chordodes 
is better known their relationships to each other cannot be deter- 
mined. As to the marine worm Nectonema agile VERRILL, while, as 
Warp (1892) has shown, it approaches closer to the Gordiacea than 
to the Nematoda, yet there are still some important differences 
between it and the former group, such as the brain appearing to have 
a dorsal ganglion, in the absence of mesenteries, and in that the sack 
containing the spermatozoa in the male (testis?) is unpaired; BURGER 
(1891) has shown that the musculature appears to be of the Nema- 
todan type. In view of these differences, and of the very incomplete 
state of our knowledge as to the genitalia, we are hardly justified 
in grouping Nectonema with the Gordiacea, as CAMERANO has 
done. 
