218 THE NORTHERN MICROSCOPIST. 
THE MICROSCOPICAL APPEARANCE OF THE 
VALVES OF DIATOMS. 
By JuLien Desy.* 
A StupDy OF THE GENUS AMPHORA. 
N the genus Amphora we meet with curious and peculiar appear- 
ances, produced entirely by the innate difference in the structure 
of the valves. ‘These cannot be better understood than by the 
use of sections and diagrammatic projections, similar to those by 
which the genus Nitzschia has already been illustrated. 
A transverse section through the centre of an isolated valve of 
Amphora presents a convex outline like a large segment of a circle. 
The valve has upon its surface a longitudinal line or raphe, smooth 
Fig. 45. 
Section through A—B, 
p-p. Small flaps (petits pans ) 
g.p. Large flaps (grands pans ) 
7. Raphe (raphé) 
and eccentric. This raphe is furnished with a small central nodule, 
or in some a stawros (a linear thickening perpendicular to the longi-* 
tudinal axis of the valve) and generally a smaller nodule near each 
extremity. This longitudinal line is in the genus Amphora some- 
times straight, but oftentimes curved or double curved, varying 
according to the species. 
* Translated from the Annales de la Socitté Belge de Microscopie, t. vi. 
Memoires, 
