Page:Popular Science Monthly Volume 6.djvu/358

344 round off the sides, and thus make two new houses out of the old one. Sometimes they build two partitions, as you see in Fig. 8, and, instead of two houses, there are four. What ingenious workers they are, thus to build four new houses out of one old one! They work so fast, too. The Chicago builders worked at the rate of a house an hour after the "great fire," but the protococcus builders can beat that, for they have been known to build one hundred thousand houses per minute, and that, too, in the winter-time, when the ground was all covered with snow!

The red protococcus, sometimes called "red snow," which is found in the arctic regions and among the Alps, will cover hundreds of acres of ground with its little red roofs in almost "less than no time." There are many curious stories told about this red snow. The ancients thought it was blood sprinkled down from heaven, as a warning of some great trouble, and it produced as much terror as comets and eclipses. But all the while it was only an innocent, pretty little plant. There is also a green protococcus that grows in the snow regions, and it is called the "green snow-plant." The red and the green snow-plants do not grow just in the same way as the protococcus of the trough or paling. The snow-carpenters divide their dwelling into a whole lot of little rooms (Fig. 9), then they "burst up" the old house entirely, and each one of the little rooms becomes a separate

mansion, and goes on doing the same thing for itself. This mode of building is called "cleavage;" the first kind is called "fission."

I told you there was a difference between the mould on the sides and the mould in the water of the old trough. You see that the protococcus mould you are looking at does not move about under the microscope, but remains quietly where you place it. Now, if you examine some of the protococcus that grows in old water, you will see the cells sculling about very fast, like so many little boats. If your eyes and microscope are very good, you can see the two tiny oars by which the little boatman guides his craft. There seem to be two kinds of boats—one small, green, and pear-shaped (Fig. 10); the others are larger, and look more like the carpenters' houses. The little pear-shaped