This view has not even been proved for _Actinosphaerium_, upon which Götte chiefly relies. The observations which we now possess merely indicate that the animal contracts to the smallest volume possible. Compare F. E. Schulze, ‘Rhizopodenstudien,’ I, Arch. f. mikr. Anat. Bd. 10, p. 328; and Karl Brandt, ‘Ueber Actinosphaerium Eichhornii,’ Inaug. Diss.; Halle, 1877. Footnote 66: The conception of Protozoa and Metazoa does not correspond exactly with that of unicellular and multicellular beings, for which Götte has proposed the names Mono- and Polyplastides. Footnote 67: Among the Rhizopoda encystment is only known in fresh-water forms, and not in a single one of the far more numerous marine forms which possess shells (see Bütschli, ‘Protozoa,’ p. 148); the marine Rhizopoda are not exposed to the effects of desiccation or frost, and thus the strongest motives for the process of encystment do not exist, at least among forms possessing a shell. Footnote 68: I trust that it will not be objected that the germ-cells cannot be immortal, because they frequently perish in large numbers, as a result of the natural death of the individual. There are certain definite conditions under which alone a germ-cell can render its potential immortality actual, and these conditions are for the most part fulfilled with difficulty (fertilization, etc.). It follows from this fact that the germ-cells must always be produced in numbers which reach some very high multiple of the necessary number of offspring, if these latter are to be ensured for the species. If in the natural death of the individual the germ-cells must also die, the _natural_ death of the _soma_ becomes a cause of _accidental_ death to the germ-cells. Footnote 69: l. c., p. 78. Footnote 70: l. c., p. 47. Footnote 71: ‘Entwicklungsgeschichte der Unke,’ Leipzig, 1875, p. 65. Footnote 72: Id., p. 842. Footnote 73: ‘Ursprung des Todes,’ p. 79. Footnote 74: l. c., p. 42. Footnote 75: ‘Contributions à l’histoire des Mesozoaires. Recherches sur l’organisation et le développement embryonnaire des Orthonectides,’ Arch. de Biologie, vol. iii. 1882. Footnote 76: l. c., p. 37. Footnote 77: Julin does not enter into further details on this point, and it is not quite clear at what precise time the cells of the ectoderm atrophy; but this is irrelevant to the origin of death, since the granular mass surrounding the egg-cells at any rate belongs to the _soma_ of the mother. Footnote 78: