Now, there can be little doubt that these forms have had ancestors that were like the other members of the group, and would have been killed had they been put at once into water of these high temperatures, therefore it seems highly probable that these forms have become specially adapted to live in these warm waters. It is, therefore, interesting to find that it has been possible to acclimatize animals experimentally to a temperature much above that which would be fatal to them if subjected directly to it. Dutrochet (in 1817) found that if the plant, nitella, was put into water at 27 degrees, the currents in the protoplasm were stopped, but soon began again. If put now into water at 34 degrees they again stopped moving, but in a quarter of an hour began once more. If then put into water at 40 degrees the currents again slowed down, but began again later. Dallinger (in 1880) made a most remarkable series of experiments on flagellate protozoans. He kept them in a warm oven, beginning at first at a temperature of 16.6 degrees C. “He employed the first four months in raising the temperature 5.5 degrees. This, however, was not necessary, since the rise to 21 degrees can be made rapidly, but for success in higher temperatures it is best to proceed slowly from the beginning. When the temperature had been raised to 23 degrees, the organisms began dying, but soon ceased, and after two months the temperature was raised half a degree more, and eventually to 25.5 degrees. Here the organisms began to succumb again, and it was necessary repeatedly to lower the temperature slightly, and then to advance it to 25.5 degrees, until, after several weeks, unfavorable appearances ceased. For eight months the temperature could not be raised from this _stationary point_ a quarter of a degree without unfavorable appearances. During several years, proceeding by slow stages, Dallinger succeeded in raising the organisms up to a temperature of 70 degrees C., at which the experiment was ended by an accident.”[27] Footnote 27: Quoted from Davenport’s “Experimental Morphology.”