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 exhibited as formed of a tangle of fibrils, or better still, of filaments or ribbons (in Greek, mitome), which are called chromatic filaments, because they are deeply stained when the cell is plunged into aniline dye. In each of these filaments, the substance of which is called chromatin, the devices of microscopic examination enable us to discover a series of granulations like beads on a string, the microsomes or bioblasts, connected one with the other by a sort of cement, Schwartz's linin, which is a kind of nuclein.

And let us add, to complete this summary of the constitution of cellular protoplasm, that it presents, at any rate at a certain moment, a remarkable organ, the centrosome, which plays an important part in cellular division. Its pre-existence is not certain. Some writers make it issue from the nucleus. At the moment of cellular division it appears like a compressed mass of granulations, which may be deeply stained. Around it is seen a clear unstainable zone, called the attraction-sphere; and finally, beyond this is a crown of striæ, which diverge like the rays of a halo—i.e., the aster. In conclusion, there are yet in the cellular body three kinds of non-essential bodies: the vacuoles, the leucites, and various inclusions. The vacuoles are cavities, some inert, some contractile; the leucites are organs for the manufacture of particular substances; the inclusions are the manufactured products, or wastes.

The Nucleus.—Every cell capable of living, growing, and multiplying, possesses a nucleus of constitution very analogous to the cellular mass which surrounds it. The anatomical elements in which no nucleus is found, such as the red globules of blood in adult mammals, are bodies which are