In Mr. Spencer's view then, the multicellular organism is not a compound being, a being compounded of adherent unicellular organisms, but a simple being, of which the cells are parts, but not absolutely essential parts, since parts of the organism may arise independently of cells. His work was written some years ago, and he does not give his authorities. I have searched every recent work I could lay hands upon, and have found no warrant for his statement that fibrous tissue ever arises independently of cells. Dr. Klein says—
"Fibrous connective tissue is developed from embryonal connective tissue cells, i.e. from spindle-shaped or branched nucleated protoplasmic cells of the mesoblast. The former are met with isolated or in bundles, as in the umbilical cord or embryonal tendon. The latter form a network as in the foetal skin and mucous membrane. In both instances the protoplasm of the embryonal connective tissue cells becomes gradually transformed into a bundle of elementary fibrils, with a granular-looking interstitial substance. The nucleus of the original cell finally disappears. A second mode of the formation of connective tissue is this: the embryonal connective tissue cell, while growing in substance, produces the fibrous tissue at the expense of its peripheral part. A remnant of the protoplasm persists round the nucleus.
"The same modes of formation of connective tissue may be also observed in the adult, under normal and pathological conditions."—Elements of Histology, p. 42.
As regards rhizopods again, I can find no warrant for the positive statement that they are not cellular. Some of them are apparently not cellular, but we have good reason for supposing that they really are so, though with the imperfect means of observation at our disposal we are unable to distinguish the cells.
In Claus's Zoology, translated and edited by Adam Sedgwick, I find—'"Nuclei are also usually present in
