The study of spirals in nature have a long history, Christopher Wren found out that many shells form a logarithmic spiral. Jan Swammerdam observed the common mathematical characteristics of a wide range of shells from "Helix" to "Spirula" and Henry Nottidge Moseley described the mathematics of univalve shells. D’Arcy Wentworth Thompson's "On Growth and Form" gives extensive treatment to these spirals. He describes how shells are formed by rotating a closed curve around a fixed axis, the shape of the curve remains fixed but its size grows in a geometric progression. In some shell such as "Nautilus" and ammonites the generating curve revolves in a plane pirpendicular to the axis and the shell will form a planer discoid shape. In others it follows a skew path forming a helico-spiral pattern.