According to other histologists, the comparison of protoplasm to a spongy mass does not give the most exact idea, and, in particular, it does not furnish the most general idea. It would be far better to say that the protoplasm possesses the structure of foam or lather. As was seen by Kunstler in 1880, a comparison with some familiar objects gives the best idea. Nothing could be more like protoplasm physically than the culinary preparation known as _sauce mayonnaise_, made with the aid of oil and a liquid with which oil does not mix. Emulsions of this kind were made artificially by Bütschli. He noted that these preparations mimicked all the aspects of cellular protoplasm. Thus, in the living cell there is a mixture of two liquids, non-miscible and of unequal fluidity. This mixture gives rise to the formation of little cells. The more consistent substance forms their supporting framework (Leydig’s spongioplasm), while the other, which is more fluid, fills its interior (hyaloplasm). However that may be, whether the primitive organization of the cellular protoplasm be that of a sponge, as is asserted by Leydig, or that of a _sauce mayonnaise_, as is claimed by Bütschli and Kunstler, the complexity does not rest there. Further recourse must be made to analysis. Just as the tissue of a sponge, when torn, shows the fibres which constitute it, so the spongioplasm, the parietal substance, is 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.