36 



BOYS AND GIRLS IN BIOLOGY. 



some of the protococctts that grows in old water, yon 

 will see the cells sculling about very fast like so many 

 little boats (Fig. 26). If your eyes and microscope are 



Fig. 26. 



Boat, or Pear-shaped Cell. 



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 shaped like a 

 pear ; the others are larger, and more like the carpen- 

 ters' houses. The pear-shaped boats have often a little 

 red window, or port-hole, which is called the "eye- 

 spot " (Fig. 27). If you watch long and carefully, you 

 can sometimes see the boatman pull in his oars as if to 

 rest (Fig. 28), and then, if you disturb or shake the 

 water and put it in the sun, out go the oars again, run- 

 ning faster than ever. They move at the rate of twelve 

 times a second ; while a watch is making one tick, they 



