38 
OF THE CHARACTERISTICS OF THE DIATOMACE^T. 
long cylindrical surface, a, b , the ‘ front view,’ * and the 
base, c, b , the 1 side view,’j* we see that the two aspects 
bear the same relation, as do the long and short axes of the 
cylinder, to each other. 
Now, if we suppose the cylinder to be divided into 
several very thin sections, a d, d e, e b, & c., in lines per- 
pendicular to its longer axis, it is clear that, so long as the 
Pig. 45. 
cr.de b d 
rows of sections remain attached to each other, the cylin- 
drical surface, a , b , appears to the eye of the observer the- 
largest, and is in fact the 4 front . 7 But the whole aspect of the 
object is changed as soon as the segments are separated 
and placed apart, as f g. Then the base exposes the 
larger surface, h , and is really the 4 front ’ to the observer. 
However, to avoid confusion, and to have fixed ideas ins 
reference to these parts, the base (or part through which the 
knife passed in our imaginary section) is held to be the 
4 side,’ while the name of 4 front ’ is appropriated to the 
part which is cut through, notwithstanding that the so- 
called 4 side ’ may be more conspicuous and more frequently 
exposed to view. As the Diatomacege propagate them- 
selves by self- division, thereby forming longer or shorter 
rows of frustules, the diagram given above affords a fair 
representation of the manner in which the frustules are 
attached by their 4 sides,’ as the collector may easily satisfy 
* This is the ‘primary’ side of Kiitzing and the ‘secondary’ of 
Rabenhorst. 
t This is the ‘primary’ side of Rabenhorst, and the ‘secondary* 
of Kiitzing ; so widely do authors differ in their nomenclature. 
