THE SEA MULLET. 97 
the kidneys can be seen through it. These are red 
in colour, situated just below the vertebral column, 
and extend along the whole length of the abdomen. 
The wreters pass backward from them, and open 
just behind the reproductive organs. 
10. Hyoid apparatus.—Cut off the head of the fish*; open 
the mouth; divide the mandibles from the maxil- 
laries ; detach the branchiostegal membrane from the 
operculum which still remains, and cut the branchial 
arches through their centres. Remove the lower 
portion. Notice the tongue supported by the basihyal, 
the urohyal going backward, and supporting the 
branchial arches on either side. From the basihyal 
proceed on each side the two ceratohyals, which 
support the five branchiostegal rays on each side, and 
these branchiostegal rays support the branchiostegal 
membrane. 
1j. The nervous system.—Hold the head in your hand, 
and with a pair of nail scissors cut off the top of the 
skull to before the eyes and down the posterior side 
of one eye. With a camel-hair brush wash away the 
loose cellular tissue that covers the brain. The brain 
is divided into three portions. The anterior is 
forined by a pair of ganglia—the olfactory ganglia— 
from which proceed the olfactory nerves; these 
nerves swell out anteriorly into a pair of ganglia in 
the nasal cavity. The middle portion of the brain 
is formed by two rather large lobes, forming the 
optic lobes, or cerebral hemispheres. Gently push 
these on one side, and observe the thick optic nerve 
going to the eye. Notice that the optic nerve of the 
* The head may with advantage be put into strong spirit for a day 
or two, but the crystalline lens will turn opaque and white. 
H 
