1. The essential protoplasm of a cell nucleus, believed in early biology to carry hereditary material; germ plasm.
Usage: biology; dated; historical term largely superseded by modern genetics terminology

Examples

• Early biologists theorized that idioplasm was the substance responsible for passing traits from parent to offspring.
• The concept of idioplasm was important in 19th-century discussions of heredity before the discovery of DNA.
• Weismann's work on idioplasm contributed to the development of modern evolutionary theory.