56 
SUPPLEMENT 
designated by the name of lobules, mammillary, cirrhous, or 
squamous, according to their form. 
The nipples, or mammilla, are elongations, more or less 
considerable, of the sides of the segment, at the extremity of 
which the seta? are implanted. Sometimes they are almost 
nothing, and then the articulations of the body are very little 
sensible ; at other times, on the contrary, they are excessively 
long, and then the body appears deeply incised throughout 
its entire length. It is those which support the lobules, of 
which we have been just speaking. 
The seta (whose structure we will give more in detail by 
and by), are stiff, hard, fragile parts, which are implanted 
more or less deeply into the skin of the chetopoda, and, in 
general, are considerably numerous. There is but a single one 
in some naides. They form simple or divided fasciculi, placed 
at the extremity of the nipple, and between the two cirri of 
the appendage. 
Modem naturalists, such as M. de Blainville, Otho Fabri- 
cius, and Savigny, distinguish three kinds of setae. 
1. The simple setae, which are slender, pointed, and straight 
at their extremity ; these are the most common, and such as 
fasciculate the best. 
2. Hooked setae, which are still rather slender, and curved, 
and terminated by a hook at their extremity. 
8. The needles, or spines ( aculei ), which are straight, like 
the simple setae, but which are always thicker, and much 
stiffer ; such are to be found in some of the aphrodite. 
We have now stated all which can enter into the composi- 
tion of the most complex appendage of a chetopoda. 
When it is not divided into two parts, one superior and the 
other inferior to the lateral line, the appendage is composed 
of a single oar. In the other case, it is in the form of two 
oars. 
