NEREIS 63 
The appendages in annelids are called parapodia. Carefully 
examine the parapodia at different parts of the body and see if 
they are all alike. 
Remove a parapodium from the middle of the body; mount 
it on a slide in glycerine or water and study it with the aid of a 
hand lens or a microscope. Compare it with the parapodia still 
on the animal and determine which is its dorsal and which its 
ventral side. It can be divided into two distinct portions, the 
dorsal and the ventral portions, called the notopodium and the 
neuropodium, respectively, each of which is stiffened by an inter- 
nal chitinous supporting rod, called the aciculum. Find the two 
acicula. The large dorsal lobe of the notopodium is a respira- 
tory organ, a gill. It contains branching blood vessels which 
can be easily seen. Attached to its dorsal edge is a slender, 
vibratile sense-organ, the dorsal cirrus. Beneath the gill are two 
lobes, one bearing bristles or sete. The neuropodium is made 
up of two lobes, one of them setz-bearing, beneath which is a 
ventral cirrus. 
Exercise 5. Draw a parapodium on a scale of 6 and label the 
parts. : 
Remove a parapodium from the hinder end of the animal, 
mount it, and study it. Has it the same parts, and if not, 
which are missing? 
Exercise 6. Draw it on a scale of 6. 
Internal anatomy. Make an incision with fine, sharp scissors 
in the mid-dorsal line of the integument of the anterior third of 
the animal, taking great care not to injure the viscera which lie 
beneath. The body will be seen to be divided into compart- 
ments corresponding to the somites, by transverse partitions 
which are called septa. Holding the cut edge of the integument 
with forceps, cut the septa where they join it, and then spread 
out and pin down the body-wall, using many pins on each side. 
