The part in which the essential nature of the organism is contained is localized in the nucleus and hence might properly be designated as nucleoplasm, as Weismann suggests.
"A Mechanico-Physiological Theory of Organic Evolution"
Carl Von Nägeli
The variety of protoplasm contained in the nucleus is called the nucleoplasm.
"Physiology and Hygiene for Secondary Schools"
Francis M. Walters, A.M.