Page:Popular Science Monthly Volume 9.djvu/485

Rh than the "uniflagellate monad," which is the fourth in the series whose life-histories were studied by Dr. Drysdale and myself. Figs. 7 and 8 will help to make this clear, where Fig. 7 is an exact rendering of Dr. Bastian's monad magnified 800 diameters; and Fig. 8 is a drawing of the "uniflagellate monad" described by my

and myself, magnified 2,500 diameters. We describe it thus: "Its exterior form is extremely simple, being ovoid, with a single flagellum. Its long diameter never exceeds the $1⁄4000$ part of an inch" in length. Now, from a very prolonged and careful study of these organisms, I am convinced that Dr. Bastian's form and ours are absolutely identical. But to make the thing simply irresistible we have further and final evidence. One of the metamorphoses of this monad on its passage to multiple fission is that it loses its flagellum, and becomes precisely what Dr. Bastian saw all around—a motionless spherule. These little bodies are less in diameter than the active monad, and of precisely the same structure. The identity is thus complete. The evidence is as full as may be; the monad Dr. Bastian saw was the one whose life-history was fully worked out. As usual, it multiplies by fission, but the fission is multiple. It then passes to a sac-like condition, resulting from the uniting together or fusion of two individuals. This sac becomes still and bursts, as seen in Fig. 4, pouring out spores that taxed our highest powers and closest watching. The spores of only two of the monads studied survived after exposure to a temperature of 300° Fahr. This is one of them.

Now, Dr. Bastian says, "A drop of the fluid containing several of these active monads was placed for about five minutes on a glass slip in a water-oven, maintained at a temperature of 140° Fahr. All the movements of the monads ceased from that time, and they never afterward showed any signs of life." This is precisely our experience. But now mark the reasoning. This monad was killed at 140° Fahr., but it was found in an infusion that had been heated up to 275° Fahr.; it must have originated de novo.