118 EMISSION OF LIGHT 
The interesting Synchata Baltica (fig. 18) be- 
longs to the tribe of Hydatinea, of which many 
individuals are common in our ditches and stag- 
nant freshwaters. 
The largest of these phosphorescent Infusoria 
described by Khrenberg, are about one-eighth o1 
a line, the smallest are from a forty-eighth to 
a ninety-sixth of a line in size. ‘They offer a 
Fig. 18. 
magnificent spectacle when placed under the mi- 
croscope in a dark room. 
Ehrenberg has likewise studied certain species 
of Photocharis, marine animalcules which resemble 
Nereis among the worms; and, when seen under 
the microscope, appear like minute strings of 
lighted sulphur. The phosphoric light they emit 
is of a greenish-yellow, similar to that of the com- 
