Page:Popular Science Monthly Volume 6.djvu/364

350 is put out as far as it can reach, then the body all runs into the foot, and another foot is stuck out from some other part, and away goes the body into this new foot. So it gets on, the feet actually swallowing

the body! The toad sometimes swallows its old skin, but the amœba is the only animal I know which is "taken in" by its feet! How odd it would be, if, as you walk along, you should suddenly disappear into your boots! If you crush the amœba, you find no trace of a tough sac such as you found in the yeast and protococcus cells. You can see nothing but the kernel or nucleus, and even that soon disappears. If you stain with magenta or iodine, the whole cell becomes colored alike. If there were a tough, woody sac, as in the yeast and mould, it would not be stained. The iodine does not give it a blue color, so there cannot be any starch in the amœbæ. The amœbæ grow like the green-mould cells, by fission, that is, by one or two partitions made through the old cells. You will first see two kernels appear in one of the old cells; then, by close watching, you see a partition going right down between the kernels, separating the old cell into two, with a kernel or



nucleus in each. Each new cell follows in the footsteps of its ancestors, crawling, eating, and growing, in the same way. And now I hope you have learned enough about this curious amœbæ family to put your wits to work and give us, some day, a full history of them, and tell us of what use they are, and what they mean by all their motions.

Boys, and girls too, sometimes, love to wade in ditches and ponds in warm weather. When you are thus wading, some time, if you will take up a piece of the duck-weed that grows on the surface of the water, you may see a number of slender green, brown, or