38 BOYS AND GIRLS IN BIOLOGY. 



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wants another dip. When they lay aside this cell-wall ? 

 or boat, they are in the same condition as animal-cells. 

 You remember, I gave the sac as one of the differences 

 between vegetables and animals. It would be strange 

 if these little creatures, like the fairies, could turn into 

 plants or animals as they please. The larger kind try 

 to be more respectable, and stay in their boats in a dig- 

 nified and proper manner. After they are killed by 

 the iodine, you can see where the little oars are pushed 

 through the row-locks in the sides of the boat. These 

 oars are called cilia, a Latin word which means eye- 

 lashes. When the little sailors are getting tired, and 

 just before they die, you can see these eyelash oars 

 very well, they move so slowly ; but, when the sailors 

 are " strong," and the day is sunny, the oars go so fast 

 you cannot see them. No Oxford or Columbia crew 

 can begin to pull with these pkotococcus boatmen. 

 They are not only very good rowers, but they are good 

 builders, too ; for you often see them breaking up the 

 old boats by cleavage and fission, just as the carpen- 

 ters break up the old houses. The mould that grows 

 on old wood and stones is called still pkotococcus ;. that 

 which moves about by oars is called moving pkotococ- 

 cus. Thus we have followed our quaint little friend, 

 the pkotococcus, through all his trades: chemist, car- 

 penter, boatman, and ship-builder. Now, I am sure, 



