these suppositions as facts in order to avoid admitting that species of living protoplasm are originated de novo in some fluids just as specks of crystalline matter originate in other fluids, and although some organisms can be seen to make their appearance in fluids independently of all preexisting visible germs, just as crystals do."
In Part III., Dr. Bastian takes up the processes of heterogenesis, whereby the matter of already existing living units gives birth to other living things, wholly different from themselves, and having no tendency to revert to the parental type. The transformations and developments represented in Figs. 3, 4, and 5, will mainly interest those familiar with the objects delineated, but they are of a very remarkable character. It is alleged that the cells of conferva give rise to euglena, a beautiful green organism which abounds in stagnant water, while this undergoes still further transformation into amœba, and ciliated infusoria. And still more surprising, if possible, is the transformation of the minute algoid chlorococcus into the large, complex, and well-known rotifer, Hydatina senta (Fig. 5).
As Dr. Bastian remarks: "The fact that animals with such distinct and specific organs should arise in this definite manner, from the reproductive products of the plant, will doubtless seem to many to flavor more of fable than of fact." This is undoubtedly true. Dr. Bastian's views contravene general experience. The derivation of organisms from preexisting germs is the actual method which we know that Nature employs in all grades from the top to the bottom of the scale of life. We know, moreover, that infusorial germs do exist, and float about, in the atmosphere. Besides, all our past knowledge of life implies the slow operation of the forces of evolution. As for the appearance of infusorial organisms in liquids, which a few hours before did not contain them, they must be explained in accordance with known modes of action, until some other method is demonstrated. To this, Dr. Bastian replies—1. That science now admits that, at some period in the earth's history, the lower forms of life have arisen by the operation of natural causes. 2. That all the considerations bearing upon the case favor the view that such organisms may be produced now, and that it is little else than absurd to suppose that "the simplest and most structureless amœba of the present day can boast a line of ancestors stretching back to such far-remote periods that in comparison with them the primeval men were but as things of yesterday;" and 3. That the de novo origin of living matter, and the transformation of low vegetable organisms into infusoria and animalcula are facts that must now be considered as experimentally established. The whole question will therefore turn on the future testing of these remarkable processes. The subject cannot be allowed to rest here; and, if Dr. Bastian's experiments shall be verified, the publication of his work will constitute an epoch in the progress of biological science. It may be remarked that the "Beginnings of Life" is written in a popular and
