224 SUPPLEMENT 
a little superior to the intestinal canal, is placed above the an- 
terior retractor muscle of the foot, applied immediately upon it, 
below the liver, against which it is cemented. It is a double 
ganglion, or divided into two lateral parts by a medial furrow, 
of a softer consistence, and more pulpy appearance than the 
other two pairs. ‘There is seen to issue forth in front a very 
fine thread, which perhaps proceeds to join the anterior gan- 
glion; a fact, however, that M. de Blainville, from whom we 
derive this information, was not able precisely to ascertain. 
Behind, there is another thread, which repairs to the muscles 
of the abdomen. 
The third pair of ganglia is altogether behind, below, and 
a little external to the anterior part of the posterior adductor 
muscle; that of one side is separated from that of the other by. 
the entire thickness of the muscle. 'They furnish, first, a very 
fine thread as a transverse commissure ; second, behind, a 
thicker thread, which penetrates into the muscle itself; third, 
from their external and posterior angle, two threads, which go 
backwards, probably to the edges of the mantle ; finally, 
from their anterior and external angle, the thick cord, by 
which they anastomose with the anterior ganglion. 
In the oscabriones the nervous system approaches more to 
what it is in the cephalophorous malacozoaria, with this diffe- 
rence, that the two lateral locomotive ganglia are replaced by 
two sorts of cords, which follow the sides of the back, and 
furnish threads to each kind of articulations. 
In the nematopods, or balani, we find almost completely the 
disposition which exists in the entomozoaria, or articulated 
division of animals, the nervous system of locomotion having 
passed below the intestinal canal, and being composed of as 
many small ganglia as there are articulations in the caudiform 
part of the body. 
At the end of a series of reproductions more or less 
repeated, the molluscous animal tends to its decomposition, 
