[36] According to Wilson (op. cit.) this was guessed by Haeckel in 1866, and confirmed in 1884-5 by the almost simultaneous discoveries of O. Hertwig, Strasburger, Kölliker, and Weismann.
[37] Sixteen have been counted in the human cell. A grasshopper has twelve, a lily twenty-four. The number is almost always an even one, but as with everything in Nature there are exceptions to the rule.
[38] The process briefly described above is that of ‘mitotic’ division (μίτος, a thread, from the appearance of the chromosomes). Amitotic division, in which the cell and nucleus simply divide in two without the formation of chromosomes, also occurs under certain conditions, but is usually an abnormal or degenerative process (cf. Wilson, The Cell, pp. 116-119).
[39] “Every animal appears as a sum of vital entities, each of which bears within itself the complete character of life” (Virchow, Cellular-pathologie, p. 12, 1858).
[40] Weismann, The Evolution Theory, I, 251.
[41] It is cast out into the cytoplasm—the substance surrounding the nucleus—where it degenerates (see Wilson, The Cell, p. 147).
[43] The Evolution Theory, I, 265.
[44] The Cell, p. 178.
[45] Scientific Papers and Addresses, II, pp. 862-3.