dition. Fig. 3 shows the direct genetic product of a third, but this sac did not contain spores, but living young, which swam forth at once upon the bursting of the sac, and by taking in pabulum at all points of the sarcode rapidly grew to the parent size. In Fig. 4 we have new features. The organism is oval, with one flagellum. It multiplies with enormous rapidity by multiple fission,[1] and then by distinct genetic union a sac is formed and spores emitted; but they are packed in a glairy fluid, and were so minute that at first our best powers
Fig. 4.
failed to reveal them. But they were afterward seen, and their full development traced. In Figs. 5 and 6 we have the same products of the last two monads. In morphological detail they greatly differed from all the preceding ones, and from each other. But the spore-sacs were produced by the same means, and the exquisitely minute spores poured forth were traced through all their stages to the adult condition.
We have here, then, important indications of fact concerning the nearest allies of the bacteria: they develop from germs.
We have, besides, the weight of the best experimental evidence pointing clearly to the existence of germs in the bacteria themselves. But the microscope has failed to demonstrate the latter. Its finest powers and finest methods failed to reach them.
Happily at this juncture Prof. Tyndall has stepped in, and, with his accustomed brilliance and precision, has opened up the path we need. He has presented us with a physical demonstration, of the existence of immeasurably minute molecules of matter—utterly beyond the reach of the most powerful combination of lenses yet constructed—which are the indispensable precursors of bacteria in sterilized infusions.[2] In short, he has opened up a new and exact method, which
