534 THE COMMON EARTH-WORM. 
Another species, the PorcUPINE SEA-MOUSE, is easily distinguished from the preceding 
creature by the peculiar structure of the back, which is devoid of the felt-like substance, 
and the scales are consequently bare. 
On account of the singular structure of the 
CH£TOPTERUS, it has been placed in a family by 
itself, of which it constitutes the sole genus. 
This remarkable worm is one of the tube- 
builders, and makes a dwelling of a tough parch- 
ment-like consistency, measuring eight or ten 
inches in length. It is found in the seas about 
the Antilles. As may be seen by reference to the 
engraving, in this curious being there is no distinct 
head, and no vestige of maxillee, but the proboscis 
is furnished with a lip, to which are attached two 
small tentacles. ‘*Then comes a dise with nine 
pairs of feet, then a pair of long silky bundles, 
like two wings. The gills, in the form of lamina, 
are attached rather below than above, and pre- 
dominate along the middle of the body.’ In the 
illustration the animal is represented in its natural 
size. 
THE next family, of which the common EArtTu- 
worm is a very familiar example, is distinguished 
by the ringed body without any gills or feet, but 
with bristles arranged upon the rings for the 
purpose of progression. 
In the well-known Earth-worm, the bristles 
are short and very stiff, and are eight in number 
on each ring, two pairs being placed on each side ; 
so that, in fact, there are eight longitudinal rows 
of bristles on the body, four on the sides, and four 
below, which enable the creature to take a firm hold 
of the ground as it proceeds. 
Except that the worm makes use of bristles, 
and the snake of the edges of its scales, the mode 
of progress is much the same in both cases. The 
whole body of the creature is very elastic, and 
capable of being extended or contracted to a won GC EEAET OTERO 5 nies eae 
derful degree. When it wishes to advance, it 
pushes forward its body, permits the bristles to hitch against the ground, and then, by 
contracting the rings together, brings itself forward, and is ready for another step. As in 
each full-grown Earth-worm there are at least one hundred and twenty rings, and each 
ring contains eight bristles, it may be imagined that the hold upon the ground is very 
strong. 
As every one knows, the Earth-worm lives a very solitary life below ground, driving its 
little tunnels in all directions, and never seeing its friends, except at night, when it comes 
cautiously to the surface and searches for company. In the evening, if the observer be 
furnished with a ‘bull’s-eye’’ lantern, and will examine the ground with a very gentle and 
cautious step, he will be sure to find many worms stretching themselves out of their holes, 
retaining for the most part their hold of the place of repose by a ring or two still left in the 
hole, and elongating themselves to an almost incredible extent. If, while thus employed, an 
Earth-worm be alarmed or touched, it springs back into its hole as if it had been a string of 
india-rubber that had been stretched and was suddenly released. : 

