PROTOPHYTES. 



45 



Petersburg, in Virginia, is such a stratum 20-40 feet 

 thick. 



5. Each kind, or species, of unicellular plants, like 

 every other organic form, has endowments or in- 

 stincts of its own. One sort remains a rounded cell, 



Fig. 18. 



or changes to a motile one. Another becomes elon- 

 gated, and distributes its coloring matter inside in 

 spiral form. Others appropriate glassy flint from 

 their food, and deposit it in beautiful patterns upon 

 their outer cell-wall. Each cell, however, in this type 

 of Protophytes is capable of independent life apart 

 from the rest, and may be considered as a complete 

 individual. 



