58 
SUPPLEMENT 
the action of the liquor in which these animals are preserved, 
and is not remarked in the first state. Some species, how- 
ever, constantly present this disposition. 
We also find, in a tolerably great number of chetopoda, 
that the first two or three rings are provided with points, or 
rather with spots, very distinct, constantly arranged in one 
manner, and which have been honoured with the name of eyes, 
though we shall presently see that there is nothing of the sort 
in their structure, and that they do not in any wise serve the 
purposes of vision. It is proper, however, to remark, that 
these points are pretty nearly constant in their number, and 
in their disposition ; so that very excellent zoological charac- 
ters may be derived from them. 
It only remains for us now to notice with respect to the ex- 
terior of the chetopoda, their colour, and the tubes or funnels 
which a great number of their species construct. 
A character which appears peculiar to this class of animals, 
and which of itself alone might almost suffice to make them 
recognized, is, that besides their proper and fixed colour, the 
epidermis, or rather the skin, properly so called, appears 
tinted with colours, irradiated with magnificent reflections of 
gold or purple. 
As to the external tube which the chetopoda often inhabit, 
although it is often sufficiently regular and solid, it cannot, 
however, in any manner be compared to the shell of the mol- 
lusca, not even when there is the greatest approximation, as 
in dentalium and siliquaria . These tubes of the chetopoda 
are always simple excretions from their body, which are by 
no means attached to it, and from which the animal may issue 
forth without dying immediately. We begin to observe 
something of this kind in the mucosity with which certain 
species line the hole, hollowed in the mud or sand which 
they inhabit, as in the arenicolm and some lumbrici. This is 
analogous to the mucous pellicle of the tube of the ampliitritag 
