MONAS. UVELLA. 83 



The genus Monas is represented in Drop II. by 

 the species M. crepusculum (fig. 1), and is curious 

 as being the smallest of known living beings. It 

 feeds on decaying substances, and may be ob- 

 served in considerable numbers, as a minute co- 

 lourless speck, moving very rapidly, by the aid of 

 a proboscis, and enjoying its transitory life in the 

 society of its kind. Another species is of a deep 

 red, and abounds in salt-marshes on the shores of 

 the Mediterranean, to which it imparts a red co- 

 lour. The M. crepuscalum cannot be seen without 

 the aid of a glass magnifying 300 diameters. 



The individuals of the genus Uvetta cluster 

 together so as to form a mass like a mulberry. 

 The species U. glaucoma is found in stagnant 

 water. Ehrenberg was able to see, within the 



