Thousands of combinations are possible between the various species of tops and bottoms, yet in the parlance of fashion only a small number of them evolve as popular combinations, or silhouettes.
Silhouettes are popular names for a particular style of swimsuit, or more precisely, for unique soutien-gorge and culotte combinations (1). The drawing depicts a sequence of bikini silhouettes from the 1940s to the 1980s, and illustrates a linear evolution within the species, as the waistline lowers and the top shrinks. The silhouettes illustrated are by no means exhaustive. Silhouettes often have popular names, and their origin and naming is often a result of their natural history and not any formal classification scheme.
Catastrophic evolution occurs when one or more of the continuous variables reaches its bounds, that is, the limits of its constraints. For example, when the leg and waistlines of the bottom collide, the collision cancels existing velocities of change and sets new accelerations in motion, often these result in a new species.
Because the top and bottom of the bikini are treated as two independent species, the concept of a silhouette is the merger of thse two individuals. With dozens of species of soutien-gorge and dozens of species of culotte, the number of silhouettes numbers in the thousands. In practice however, certain top/bottom combinations seems to emerge as fashion favorites at different points in time. See BSD8803 for Barthes' concept of genus and species of swimwear.
Judson Rosebush, Bikini Science Hypercard Stack, 1988. 1 picture.