In the realm of volatile objects, several small configurations were
found which were capable of expanding hundreds or even thousands of
generations before settling down into a stable ending. One of these, of
seven cells, resembling the greek letter 
, occurs frequently in
general evolutions; its second generation, sometimes called a
``thunderbird,'' is also common. Not only are they of frequent
occurrence; their expansion is quite aggressive, although the region of
evolution usually collides with other regions in the field and soon
loses its identity.
Figure: First and second generations of a very volatile object.