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In all the higher forms, however, the segregation is well marked, and a “nuclear membrane” separates the substance of the nucleus, or “karyoplasm”6 from the surrounding “cytoplasm.”

Within the nuclear membrane the karyoplasm is differentiated into two very distinct portions, a clear fluid portion, the “karyolymph,” and a firmer portion in the form of a coarser or finer “nuclear reticulum.”