44 EASY LESSONS IN VEGETABLE BIOLOGY. 



built like a spider's web, and is applied to the genus. 

 The second word refers to the name of a distinguished 



naturalist, and names the species the Arachnoidiscus 

 of Ehrenberg. This example illustrates how the vari- 

 ous kinds of organisms are named. 



In Fig. 18 there are examples of three other kinds 

 of diatoms. 



In the living state diatoms are found abundantly in 

 every pond, rivulet, ocean, and rock -pool. They 

 often make immense deposits by their rapid multi- 

 plication, and in a fossil state they form large strata 

 of rock material. Under the cities of Richmond and 



