56 VERMES. 
The length of the specimen was fifteen or sixteen inches, breadth 
an inch, and thickness about a quarter of an inch ; the whole of a flat- 
tened form, nearly linear, diminishing slightly both im breadth and 
thickness towards the posterior extremity, which, like the anterior, is 
obtuse. A thin border environs the body, which, sundered transversely, 
is elliptical. 
The anterior margin of the animal is cleft horizontally in front by 
a shallow groove, deepening as it descends some way down each side of 
the head ; and there is a dilateable slit, a quarter of an inch long in the 
under surface, near the extremity of the head, denoting the mouth. 
Colour universally grey, darker on the upper surface ; the thin border 
and under surface lighter. 
No specks or eyes were perceptible. 
This animal swims very actively in long, smooth undulations, the 
edge or margin of the body being uppermost during its course around 
the interior of its vessel, which will sometimes continue for hours. But 
I cannot speak of its precise position, either in a vessel of large capacity, 
or in the sea, not having witnessed it in either.—Plate VI. fig. 1. Gordius 
in motion ; fig. 2. transverse section, shewing the figure of the body. 
Plate VII. fig. 1. under surface of anterior portion, shewing the form 
and position of the mouth, and the marginal groove. 
After its lively exercise on the second evening, I found the animal 
contracted, motionless, and apparently dead next morning, which was 
the subject of no little regret, from not having had an opportunity of 
obtaining a correct delineation, always so important in illustrating natu- 
ral history. It allowed itself to be lifted by the hand without the least 
resistance ; yet, when committed again to recent sea water in another 
vessel, all its activity was resumed, which continued till a late hour of 
the night, when both then, and from subsequent observation, I concluded 
it to be of nocturnal habits. 
The alternate activity and quiescence of this creature are alike singu- 
lar. Instead of the languid exertions and tardy motions common to the. 
vermicular genera, the gradual unwinding of the sluggish bodies of 
some, and the extension of others from their secret retreats, the Gordius 
