Q.State the protoplasm theory

Step 1. Trace how the idea developed. Corti was the first to actually observe this living substance. In 1835, Felix Dujardin described a living, jelly-like content inside animal cells and named it 'Sarcode'. In 1839, Jan Purkinje separately coined the term 'protoplasm' for the equivalent substance inside plant cells. Hugo von Mohl (1846) argued for its importance.

Step 2. State the theory itself. In 1861, Max Schultze showed that Sarcode and Protoplasm were, in fact, the same kind of living material regardless of whether it was found in an animal or a plant cell, and proposed a unifying theory around this - a theory that Oscar Hertwig formally named the 'Protoplasm Theory' in 1892. Thomas Huxley (1868) captured the theory's central claim memorably by calling protoplasm the 'physical basis of life': the idea that this one substance, wherever it occurs, is what actually makes a cell alive.

Step 3. State what protoplasm is understood to be. Chemically, protoplasm was later shown (Fisher, 1894; Hardy, 1899) to be a complex colloidal system - mainly water, carrying true, freely dissolved (crystalloid) solutes such as sugars, salts and acids, together with colloidal solutes such as proteins and lipids. …

Trace the historical development of the idea (Dujardin, Purkinje, Schultze, Hertwig, Huxley) and then state the theory's core content - protoplasm …

• Naming only Hertwig (who named the theory) or only Huxley (who gave its famous phrase) while omitting Schultze, who is the scientist who actually proposed the unifying theory itself in 1861. …