The adult organisation of Paragordius varius. 393 
together, might serve to attach the animal more firmly to plants when 
in the free state. Now in the genus Gordius, tubercles and hairs are 
limited to the male, and to the region of the cloacal aperture and 
the inner surface of the tail lobes; in Paragordius to the male, to the 
inner surface of the tail. lobes, and the mid-ventral region of the 
trunk; in Chordodes they occur in both sexes, and are found over the 
greater surface of the body. Perhaps this series may be a parallel 
to their phylogenetic development. In that case they would have first 
arisen in the vicinity of the cloacal aperture of the male, and hence 
their first function would have been to hold the female in copulation 
(which is accomplished in the Nematodes by means of spicula). From 
that part they have come to extend over the ventral surface forwards, 
then over the whole surface of both sexes. Presumably such tubercles 
would irritate the internal organs of the host much more than a 
smooth tubercle; and since such tubercles are developed towards the 
close of the parasitic stage (the first cuticle being smooth), they might 
hasten the death of the host so as to allow the quicker escape of the 
worm; in that case they might have been fostered in the genus Chor- 
dodes by natural selection. 
Literature on the cuticula. The external cuticula has 
been treated to some extent by all describers of species of Gor- 
diacea; for the external sculpturation offers fairly good specific 
differences, as VırLor (1874) first pointed out. It is not necessary 
to repeat these descriptions of mere surface views, VEJDOVSKY (1886, 
1894) distinguishes two layers of the cuticula; the outer “homogene”, 
and the inner “faserige”; pore canals and sense hairs are described. 
VırLor (1874, 1887) uses for the outer cuticula the term “epiderme”, 
for the inner, “derme”. CAMERANO (1888a, b, 1897b) distinguishes in 
the “cuticula” a “strato esterno” and a “strato fibrillare”; he also 
finds pore canals. von Linstow (1889) uses the term “Cutis” for the 
fibrous layer of the cuticle, and “Epidermis” for the outer layer. 
IT. The Hypodermis. 
The hypodermis of the female has been studied more carefully 
than that of the male, and the following description applies to the 
female unless otherwise stated. 
The hypodermis (Hyp of the figures) lies immediately beneath 
the cuticle, and at the posterior end of the body is continued inwards 
as the epithelial lining of the cloaca. It is thickest in the ventral 
26* 
