102 THE AMERICAN MONTHLY [Apr 



being formed of the so-called f rustules. Ou the other or, 

 as it is called, the side view, it is of course round. But 

 as ou the front view, the frustules are more or less round- 

 ed, it becomes a sphere. 



We must remember that we are looking at it in the pre- 

 pared state, the Diatom, when the matter which forms it 

 has been removed. Thus, we might liave a man seen when 

 he is dead and has been dead some time. In that cage, 

 we would have merely the skeleton left to name. This 

 would be very diflFerent from the man himself and it would 

 be idle to define man himself from the skeleton alone. But 

 the skeleton of man is internal and the skeleton of a Ba- 

 cillarian seemingly external. Nevertheless, to describe a 

 Bacillarian in toto w© must describe the skeleton and the 

 internal parts also. Therefore we must describe the frus- 

 tules and, if it is present, the connecting membrane like- 

 wise. 



Cyclotella appears growing in fresh-water everywhere. 

 When it grows or increases in volume, it does not do so 

 by increase in the size of the individual, for that could not 

 be, as the skeleton is of hard matter and cannot increase in 

 bulk ; but it grows by forming a new individual, which, 

 for a time, is attached to the first individual and then be- 

 comes free. Another genus, as it is called, of Bacilliaria 

 is very common in streams and on the shore of the ocean 

 everywhere. In fact, it is more common than that al- 

 ready described. Thi.s is known as Melosira. But this 

 occurs as a chain of long threads of spheres and is com- 

 monly supposed to be a sea-weed or fresh-water plant or 

 alga. 



. 3Ielo8ira varians is very very common being found in 

 fresh-water streams sometimes that run swiftly. It is 

 found in the brackish water of marshes and then becomes 

 Melosira nummuloides. It has been brought down by the 

 streams where it grows as Melosira varians and is evolu- 

 ted into Melosira nummuloides. It grows as Melosirj* 



