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THE POPULAR SCIENCE MONTHLY. 



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, in- 

 stead 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 an- 

 cients thought it was blood sprinkled down from heaven, as a warn- 

 ing of some great trouble, and it produced as much terror as com- 

 ets 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 



- Old cell. 

 New cells, or rooms. 



Fig. 9. Snow-Carpenters dividing the Old 

 House into New Kooms by Cleavage. 



Fig. 10. -Boat, or Pear-shaped Cell. 



mansion, and e^oes on doing: the same thingr 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 proto- 

 coccus mould you are looking at does not move about under the micro- 

 scope, 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 w T hich 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 



