a protecting investment of fibres resembling areolar tissue to both structures. This is certainly a very striking comparison, but the external investment must not in either instance be regarded as a something unessential, as a structure composed of other elementary parts, for the ganglion-globules, like the yelk, are true cells, and their external covering is an essential component part of them; it is the cell-membrane. The vitelline membrane of the bird’s egg, while contained in the ovary, is perfectly structureless, not composed of more minute ele- mentary parts; the same is the case with the investment of the ganglion-globules. They are both of them true simple cells. The parenchyma of the ganglion-globules forms the cell-con- tents, and the vesicle in their interior is the cell-nucleus ; the small corpuscles which it contains are the nucleoli. The vesicle of the ganglion-globules lies, as in other cells, eccentrically upon the internal surface of the cell-membrane. This cell- membrane may be most distinctly observed in the ganglion- globules of the sympathetic nerves of the frog, previous to their junction with the sacral plexus. (See pl. IV, fig. 10, a.) It there appears comparatively dark, and sharply defined, both externally and internally, so that its thickness may be readily measured. Valentin has already remarked, that the capsule of the gan- glion-globules is thicker in the lower animals. In the situation before mentioned in the frog, it seems as though a ganglion- globule were sometimes formed within another cell. (See fig. 10, b.) The ordinary contents of these ganglion-globules is a minutely-granulous, yellowish substance. On one occasion, however, I saw a ganglion-globule from the head of an ox (I do not precisely know from what part it was taken), in which the granulous appearance was confined to the surface, the interior being clear,—a fact which was rendered distinctly perceptible by causing the globule to roll about. It is nothing remarkable that two nuclei should sometimes occur in one ganglion-globule; we have observed this already in several cells, in those of cartilage for instance. In those instances, however, only one of them was the true cell-nucleus, the cytoblast of the cartilage-cell, the other being a subsequent formation within the cell.
