Remove the thin membrane stretching over the abdomen and in which the heart and tracheal "Vs" lie, and note immediately underneath it the large coiled _intestine_ with a knot of greenish yellow threads in the centre. Carefully uncoil and pin out the intestine, cutting away the tying tracheæ, but being careful not to cut other structures. Work out the full length of the alimentary canal, noting the _œsophagus_, the widened _crop_ behind it, and the long intestine. From the intestine arise several greenish yellow threads, the _Malpighian tubules_. These are the excretory organs of the insect. What is the total length of the alimentary canal? The reproductive organs, consisting of a pair of glands (egg-glands or sperm-glands) with a pair of tubes which unite before reaching the body-wall and have a common external opening, may now be seen. These should be removed, thus exposing the _ventral nerve-chain_ in the abdomen. To expose the chain in the thorax it will be necessary to pick away carefully the muscles. As in the crayfish, the central nervous system in the beetle consists of a ventral nerve-chain, a _brain_ or _supra-œsophageal ganglion_ and a pair of _circum-œsophageal commissures_ connecting the brain and the foremost ganglion (_infra-œsophageal_) in the ventral chain. There are, in the ventral chain, four ganglia in the thorax and four in the abdomen. The large nerves running from the brain to the compound eyes and to the antennæ can be traced. Make a drawing showing the nervous system.