es NGG 
. i 
1905| Tue Hair-£EL. 137 
to the Nematoidea or thread worms by its alimentary canal. and 
in the nature of its secreting glands to the larva (Cercaria) of 
Trematodes.” It enters the body of a water-snail, such as 
Lymnea or Planorbis, but has also been found in the frog, fishes, 
aquatic insect larve, and in these it becomes encysted, or encased 
in a hard capsule. A second form of Gordius larva, more elong- 
ated and without head-armature, has been described in the body 
cavity, outside the intestine, of Dydzscus, the large water-beetle, 
Carabus, spiders, certain fishes and amphibians ; and it was ob- 
served to move freely amongst the internal organs of its host. 
Later it loses its larval features and distinctively ento-parasitic 
habits, and takes on the form and free life of the adult. The 
larval life has been stated to last five or six months, at the end of 
which time it doubles its length, loses its spines, becomes swollen 
and soft : but on attaining a length of two inches the skin hardens, 
and the dark brown or black color is assumed. 
If naturalists still disagreee in their descriptions of the min- 
ute structure and anatomy of Gordius, and if there is some incon- 
sistency in the existing accounts of its larval development and 
adult habits, it might be anticipated that its zoological position 
had been decided beyond dispute. But this is not so. It has 
been usual to group the Gordiide, Mermide, and Spherularide, 
in the order Gordiacea, alongside the order Nematoda, in the class 
Nematelmia ; others place them amongst the thread-worms or 
-Nematodes with which they agree in many important particulars ; 
but other authorities remove them altogether, and regard them as 
aberrant, and not closely allied to the parasitic worms mentioned. 
The Nematode worms, it is true, are cylindrical animals, tapering 
towards each end, and never divided, like so many groups in the 
sub-kingdom Vermes, into segments or successive joints ; and the 
Gordiide agree in this total absence of metamerism or segmenta- 
tion: but in their minute structure they exhibit as many diverse 
features, as features of resemblance, and further study is necessary 
to establish the position and real character of the Hair-eels. 
Even their alleged survival after long periods of dessication needs 
