116 EMISSION OF LIGHT 
highly magnified; 2, less magnified; 5, as seen 
with a pocket lens on the surface of a glass of 
water; 4, as they descend through the water, 
glowing with phosphorescent lght, when the 
olass is shaken.) 
In the year 1830, Michaelis, a distinguished 
professor at Kiel, was, according to Humboldt, the 
first to make known the existence of Phosphoric 
Infusoria.. He first observed the phenomenon 
of phosphorescence in a species of the genus 
Peridimum (fig. 15), a ciliated animalcule, and 
igo ds 
afterwards in Prorocentrum micans,* and in the 
* Tt is exceedingly probable that this animalcule will be placed 
among the Rhizopodes; and the same remark may apply to 
many now-called Infusoria. In this microscopic class of ani- 
mals, as it undergoes fresh investigations, the species are con- 
tinually being removed and placed in higher genera, families or 
classes. Thus the Rotifera are now classed among the Annelides. 
