Note 87 — THE FORMS AND COLOURS OF LIVING CREATURES.

There is an ambiguity in the use of the word “cell.” By some writers it is only used to denote a particle of protoplasm with a nucleus (whether or not it is enclosed in a “cell-wall”), while such a particle without a nucleus is called by them a Cytod. By others it is used to denote any particle of protoplasm enclosed in a cell-wall, and by others, again, as denoting any distinct particle of protoplasm with or without a nucleus, and with or without a cell-wall. It is in this widest sense that it is here proposed to use the term “cell,” distinguishing, where needful, those with a nucleus or envelope as “a nucleated” or “a walled” cell.

As yet the two natures and functions of the nucleus and nucleolus are by no means cleared up. The nucleus often appears to contain a complexity of fibrils, transitory aggregations of which have been supposed to cause the appearance of nucleoli. The apparently simplest protoplasm is probably of really very complex, most minute structure.