Fiveand six-membered rings are the most stable and important, the last-named group resulting from the polymerization of many substances; threeand four-membered rings are formed with difficulty, and are easily ruptured; rings containing seven or more members are generally unstable, and are relatively little known.
True ring systems, which possess the characters of organic nuclei, do not come into existence in threeand four-membered rings, their first appearance being in penta-atomic rings.
Six-membered ring systems can be referred back, in a manner similar to the above, to pyrone, penthiophene and pyridine, the substances containing a ring of five carbon atoms, and an oxygen, sulphur and nitrogen atom respectively.
Proceeding to the six-membered hetero-atomic rings, the benzo-, dibenzoand naphtho-derivatives are frequently of great commercial and scientific importance.
The House of Assembly consists (as originally constituted) of 121 members, elected by single-membered constituencies, each constituency containing as nearly as possible the same number of voters.