extremity; by this means a hollow fpace is formed, and the
bladder of air pent up in it looks like a pearl, Fig, 2, Plate XI.
It is by die afliftance of this bubble, or little balloon, that the in-
fe£l raifes itfelf again to the furface o f the water. I f this bubble
efcapes, it can replace it from the pulmonary tubes ; fometimes
large quantities o f air may be feen to arife in bubbles from the
tail of the worm to the furface o f the water, and there mix with
the incumbent atmofphere. This operation may be 'eafily feen
by placing the worm in a glafs full o f water, where it will afford
a very entertaining fpeftacle.
The fnout is divided into three parts, o f which that in the
middle is immoveable; the two other parts grow from the fides
o f the former; thefe are moveable, vibrating in a very rfingular
manner, like the tongues of lizards and ferpents. The greateft
ftrength o f the creature is fixed in thefe lateral parts o f the fnout;
it is on thefe that it walks when it is out o f the water, appearing
as it were to walk on it’s mouth, ufing it, as the parrot does its
beak, to move (climb) with greater advantage.
We lhall now confider the external figure o f this worm, as it
appears with the microfcope. It is frnall towards the head, larger
about thofe parts which may be'confidered as the thorax, jt then
grows fmaller, converging at the abdomen, terminating in a
{harp tail, furrounded with hairs in the form of the rays o f a
ftar.
This worm, the head and tail included, has twelve annular
divifions, 1, 2, 3, 4, 5, 6, 7 ,8 ,9 , 10, 11, 12, Fig. 3, Plate XI.
It’slkin refembles the covering of thofe animals that are provided
with
223
with a cruftaceous habit, more than it does that o f naked worms
or caterpillars ; it is moderately hard, .and like the rough Ikin called
fhagreen, being thick fet with a number of grains, evenly diftri-
buted. The fubftance of the {kin is firm and hard, and yet very
flexible.
On each fide o f the body are nine fpiracula, or holes, for the
purpofe of refpiration; there are no, fuch holes vifible on the
tail ring a, nor on the third ring counting from the head ; for at
the extremity o f the tail there is an opening for the admiflion and
expulfion of a ir : in the third ring the fpiracula are very frnall,
and appear only under the {kin, near, the place where the embryo
wings of the future fly are concealed. It is remarkable that caterpillars,
in general, have two rings without thefe fpiracula; perhaps,
becaufe they change into flies- with four wings ; whereas
this worm produces a fly that has only two.
The fltin has three different {hades o f colour; it is adorned with
oblong black furrows, with fpots o f a light colour, and orbicular
rings, from which there generally fprings a hair, as in the figure-
before us, only the hair that grows on the infeft’s fide is represented;
befides this there are here and there fome other larger
hairs c c. The difference of colour in this worm arifes from the
quantity of grains in the fame fpace; for in proportion as there
is a greater or leffer quantity of thefe, the furrows and rings are
o f a deeper or paler colour.
The head d is divided into three parts, and covered with a
fkin, the grains on which are hardly difcernible. The eyes are
rather protuberant, and lie forwards near the fnout. It has alfo
two