[1] Guettard and Gérard de Villars. Bernard de Jussieu also, who demonstrated that starfish can regenerate. [2] An annelid of unknown species. [3] This statement of Spallanzani’s I interpreted incorrectly (’99), thinking that he obtained a two-tailed form as had Bonnet. [4] There is some doubt in regard to this statement of Spallanzani’s. In a letter to Bonnet he denies that this takes place in the earthworm. [5] Spallanzani refers to the work of Ginnani, Vandelli, Vallisneri. [6] He found that the legs of the tadpole of the frog, and of two species of toads, also have the power of regeneration. [7] These experiments on the earthworm are in the main taken from my own results (’95) (’97) (’99). [8] _Lunularia vulgaris._ [9] Gesammelte Abhandlungen, No. 27, p. 836. [10] The fact that the piece does, or does not, take in food has no bearing on the question, since many animals that do not feed while the regeneration is going on produce new cells to form the new part. [11] These two kinds of regeneration are post-generation and regeneration proper. The distinction that Roux attempts to make between these two processes is to a certain extent artificial and rests at present on a very unsafe basis, at least in so far as the post-generation of the frog’s embryo is taken as a representative case of this process. Roux states that in the process of _regeneration_ the injured tissues produce each their like in the new part, while in the process of _post-generation_ of the frog’s egg the new cell-material arises in part from the nuclei and yolk-material of the injured half and in part through the accidental position of the nuclear material of the uninjured half. In order more fully to understand this distinction the original description of the process of post-generation given by Roux in his account of the development of half embryos of the frog’s egg must be referred to. In later papers Roux pointed out that the missing half of the frog embryo, as well as of other forms, may be post-generated without any new material appearing at the open side of the embryo. It is unfortunate, I think, that the original term should have been extended to include these other processes that do not partake of the nature of post-generation as at first defined, but are more like the true process of regeneration as described by Roux. [12] Ergebnisse der Anatomie und Entwickelungsgeschichte. 1891-1900. [13] As used in connection with other terms, see his Ges. Abhandl., Vol. II, page 41. [14] Die Zelle und die Gewebe. [15] Hertwig’s description of the method by which a piece of hydra makes a new one shows that he did not understand the kind of change that takes place in this animal. [16] Organographic der Pflanzen, ’98. [17] This term is used by Driesch to his _Analytische Theorie_. [18] Delage, Y. _La Structure du Protoplasma_, etc., ’95. [19] The dark red glass was fairly monochromatic; the dark blue let a trace of red light through.