44. BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 
and it has been found characteristic for all the males of Chordodes which have 
been heretofore described. The characters of these three genera of Gordiacea 
may be compared as follows. 
Gordius. Posterior end of the male bilobed, a cloacal musculature present; 
posterior end of the female rarely much swollen, never cleft (except in G. tolo- 
sanus, where it is deeply grooved rather than cleft); the caudal ganglion in the 
female not in contact with the cloacal epithelium, the cloaca very short; cu- 
ticula marked with intersecting lines or with low areola, never with high tuber- 
cles or papillæ, though frequently with short hairs or conical processes (spicules), 
Chordodes. Posterior end of the male not bilobed, but only with a compara- 
tively shallow groove on the ventral surface; posterior end of the female usu- 
ally swollen, never cleft ; the caudal ganglion in the female not in contact with 
the cloacal epithelium, the cloaca very short; the male with a special cloacal 
musculature; cuticle usually marked with high tubercles or papille, and 
apparently always with hyaline club-shaped processes, which are very differ- 
ent from the interareolar hairs of Gordius. 
Paragordius. Posterior end of the male bilobed, no cloacal musculature ; 
posterior end of the female trilobed ; the caudal ganglion in the female is in 
contact with the cloacal epithelium, and the cloaca is long; cuticle as in Gor- 
dius, except that the papilla are enveloped in a hyaline layer, which forms the 
external layer of the cuticle (Fig. 91, a). 
These three genera appear to be very natural groups, and each is to be dis- 
tinguished by the union of certain characters, rather than by the presence of 
any single character. Of the three, Gordius occupies an intermediate position, 
with relations on the one hand to Chordodes, on the other to Paragordius, 
though it shows the greater affinity to Chordodes ; while there are no good 
characters in common between Chordodes and Paragordius. Thus Gordius 
might be regarded as the more primitive parent form, from which the others 
have differentiated ; but I reserve a discussion of this point for a subsequent 
contribution. 
The following preliminary note on the caudal ganglion of Paragordius (in 
the female) may be of anatomical interest. This ganglion lies in contact with 
the cloacal epithelium at the anterior point of bifurcation of the two lateral 
tail lobes (Fig. 79). The posterior margin of this ganglion forms a thin verti- 
cal lamina, which may be in contact with that portion of the epidermis lying 
between the two lateral lobes, but it certainly does not terminate in contact 
with the epidermis of the ventral surface of the body. The ventral nerve 
chord anterior to the caudal ganglion lies in the ventro-median line between the 
intestine and the longitudinal musculature of the body wall, as in both Gordius 
and Chordodes, as far as the latter genera have been examined. But there are 
certain small nerves which take their origin from the antero-dorsal margin of the 
caudal ganglion, and these nerves lie directly beneath the cloacal epithelium. 
These relations were studied on sections of two females; and anterior and pos- 
terior nerves may be distinguished with reference to the course which they pur- 
sue. The anterior nerves, which are of greater diameter than the posterior 
