244 
SUPPLEMENT 
the assemblage of the composite eyes. From the lower face 
of the brain, originate four other nerves, which go to the an- 
tennae, and which give out some threads to the neighbouring 
parts. From its posterior edge, spring two very elongated 
nervous cords, which comprehend the oesophagus between 
them, and unite underneath, in an enlargement or medial 
ganglion, and which give out towards the middle of their 
length, a thick nerve which repairs to the mandibles and to 
their muscles. The ganglion inferior to the oesophagus, fur- 
nishes the nerves which proceed to the jaws, and to the jaw- 
feet.” 
“ In the astaci , and the other macrourous decapod Crus- 
tacea, the two cords remain inter-approximated throughout 
the entire length of the body, and form there five successive 
ganglia, placed between the articulations of the five pairs of 
feet. Each foot receives a nerve from the ganglion, which 
corresponds to it, and this nerve penetrates as far as its 
extremity. That of the claw, or forceps, is the thickest. 
The medullary cords, when arrived at the tail, unite so in- 
timately that it is no longer possible to distinguish them. 
They form then six ganglia, of which the first five furnish 
each two pairs of nerves. The last produces four, which are 
distributed in radii to the scaly fins that terminate the tail.” 
In the crabs all the anterior part of the nervous system is the 
same, but the two oesophageal cords are united a little more 
backwards than in the astaci. “ They are,” continues the 
Baron, u in the middle of the thorax, and there commences 
a medulla, shaped like an oval ring, grooved in the middle, 
and eight times larger than the brain. From the circum- 
ference of this ring spring the nerves which proceed to the 
different parts. It furnishes six nerves on each side for the 
jaws, and the five feet, and there is an odd one which comes 
from the posterior part, and repairs to the tail. It represents, 
as it were, the ordinary knotty cord ; but its ganglia, if it have 
