460 THOS. H. MONTGOMERY jr., 
large nerves which penetrate the capsule of the eye and ramify there. 
There is thus no ring of nerve cells around the oesophagus as in the 
Nematoda, nor yet a cerebral ganglion as in the Annelida; but 
the anterior end of the central nervous system is on the whole unique 
in its structure. The ventral nerve cord is connected with the under- 
lying neural lamella, through which nerve fibres pass to the hypo- 
dermis. VEJDOVSKY found that in Gordius this lamella is more or 
less interrupted, but in Paragordius I find it to be a continuous, un- 
broken lamella beneath the whole extent of the nerve cord. There 
are thus no segmental attachments of it to the hypodermis, and the 
nerve fibres within it are neither paired nor segmentally arranged. 
The nerve cells also (of which there are two kinds) of the central 
nervous system do not show a paired distribution nor segmental ar- 
rangement (in the form of ganglia), but succeed each other continu- 
ously along the whole extent of the cord. The adult structure shows 
the nerve cord to be an unpaired and unsegmented structure, with 
the nerve cells arranged ventrally and laterally, and with one un- 
paired and three paired fibre tracts; and Veypovsky from embryo- 
logical studies regards the first origin of the nerve cord as unpaired. 
Thus the type of the nervous system is entirely different from that 
of the Annelida. It differs also from the Nematodan nervous system 
in that in the latter there are (at least in the anterior portion of the 
body) two median and two lateral nerve trunks. The fact that the 
Gordiacean nerve cord shows a more or less tripartite structure would 
suggest that it might represent a possible coalescence of a ventral 
with a pair of lateral nerve trunks, and thus be referable to the Nema- 
todan type; but this is improbable, for the neural lamella connecting 
with the hypodermis is a strictly unipartite structure. The occurrence 
of true nerve cells in the hypodermis, particularly in the dorsal region, 
shows the nervous system to be of rather a diffuse type; and in 
general it may be considered unique, and not referable to that of 
Annelida or Nematoda. 
We now come to an organ system that has gradually come to 
be regarded as of great importance in anatomical comparisons, the 
genital system. In the Nematoda the essential organs are, in the 
female, a pair of long, non-segmented tubes, the ovaries, and of con- 
tinuations of the latter, the oviducts, which open by means of an un- 
paired vagina generally on the ventral surface of the body at a con- 
siderable distance anterior to the anal aperture; in the interesting 
genus Cloacina alone, as described by von Linsrow (1897b), does the 
