Spirograph Spirograph Spirograph is a geometric drawing toy that produces mathematical roulette curves of the variety technically known as hypotrochoids and epitrochoids. It was developed by British engineer Denys Fisher and first sold in 1965. The name has been a registered trademark of Hasbro Inc. since 1998 following purchase of the company that had acquired the Denys Fisher company. The Spirograph brand was relaunched worldwide with original product configurations in 2013 by Kahootz Toys. In 1827 English architect and engineer Peter Hubert Desvignes developed his "Speiragraph", a machine to create elaborate spiral drawings, intended to prevent bank note forgeries. The mathematician
Fisher's geometric model Fisher's geometric model Fisher's geometric model (FGM) is an evolutionary model of the effect sizes and effect on fitness of spontaneous mutations proposed by Ronald Fisher to explain the distribution of effects of mutations that could contribute to adaptative evolution. Sometimes referred to as the Fisher-Orr model, Fisher's model addresses the problem of adaptation (and, to some extent, complexity), and continues to be a point of reference in contemporary research on the genetic and evolutionary consequences of pleiotropy. The model has two forms, a geometric formalism, and a microscope analogy. A microscope which has many knobs to adjust the lenses