What has been called the revivification of Rotiferæ, since observations have been more exact and have had to undergo stricter criticism, has been the subject of much animated discussion. Baker affirmed that he had resuscitated, in 1771, paste-eels which Needham had given him in 1744! Franz Bauer saw his Vibrio tritici, which had been dried up for four years, move again on being moistened. An extremely careful and experienced observer, Doyère, in his Mémoire sur les Tardigrades, et sur leur propriété de revenir à la vie (1842), draws from his own fine experiments the following conclusions:--Rotiferæ come to life, _i. e._ pass from a motionless state to a state of motion, after having been exposed to temperatures of 19°.2 Reaumur below, and 36° Reaumur above, the freezing point; _i. e._ from 11°.2 to 113°.0 Fah. They preserve the capability of apparent revivification, in _dry sand_, up to 56°.4 R. (158°.9 Fah.); but they lose it, and cannot be excited afresh, if heated in _moist sand_ to 44° only (131°.0 Fah.) Doyère, p. 119. The possibility of revivification or reanimation is not prevented by their being placed for twenty-eight days in barometer tubes in vacuo, or even by the application of chloride of lime or sulphuric acid (pp. 130-133). Doyère has also seen the rotiferæ come to life again very slowly after being dried without sand (desséchés à nu), which Spallanzani had denied (pp. 117 and 129). “Toute dessiccation faite à la température ordinaire pourroit souffrir des objections auxquelles l’emploi du vide sec n’eût peut-être pas complètement repondu: mais en voyant les Tardigrades périr irrévocablement à une température de 44°, si leurs tissus sont pénétrés d’eau, tandis que desséchés ils supportent sans périr une chaleur qu’on peut évaluer a 96° Reaumur, on doit être disposé à admettre que la revivification n’a dans l’animal d’autre condition que l’intégrité de composition et de connexions organiques.” In the same way, in the vegetable kingdom, the sporules of cryptogamia, which Kunth compares to the propagation of certain phænogamous plants by buds (bulbillæ), retain their germinating power in the highest temperatures. According to the most recent experiments of Payen, the sporules of a minute fungus (Oïdium aurantiacum), which covers the crumb of bread with a reddish feathery coating, do not lose their power of germination by being exposed for half an hour in closed tubes to a temperature of from 67° to 78° Reaumur (182°.75 to 207°.5 Fah.), before being strewed on fresh perfectly unspoilt dough. May not the newly discovered monad (Monas prodigiosa), which causes blood-like spots on mealy substances, have been mingled with this fungus?