96 DESCRIPTION OF [Polygastrica. 



31 UVELLA glaucoma. The glaucous Uvella (Volvox so- 

 cialiSy M.) Form oval, but inclining to conical, with the 

 posterior extremity attenuated as it advances in age. Hya- 

 line, with large ventricles, and evidently two filiform probos- 

 cides. In 1831, Ehrenberg first observed a vibration at its 

 anterior part, and its reception of coloured food. In 1835, 

 he discovered within the body of this minute creature 

 some green Monads which it had eaten, and by which it 

 was proved to subsist by prey. When fed on indigo, as 

 many as twelve stomachs were filled, and it has been some- 

 times seen to void little blue particles, which seemed like 

 undigested matter, from its mouth. With a power of 800 

 diameters a great number of small colourless granules, 

 having the appearance and form of eggs, may be discerned, 

 lying between the nutritive sacs. It increases both by a 

 transverse and longitudinal section. Engraving, group 3, 

 represents a cluster of these creatures ; figures 4 and 5, 

 separate young ones ; and 6, an old one. They are mag- 

 nified about 350 diameters. The individuals, when full 

 grown, are elongated, and their ova may be perceived with 

 800 linear. Ehrenberg has seen them prey on the green 

 Chlamidomonas. Found in water-butts. Size l-2300th to 

 1 -2350th ; diameter of cluster l-430th. 



32. UVELLA bodo. The green Uvella. Fore part of 

 the body rounded, attenuated posteriorly. It is of a beau- 

 tiful green colour ; found in stagnant water. Size 1 -4030th 

 to l-3450th; diameter of cluster l-2350th. 



Genus III. POLYTOMA. The Partile Monads. This 

 genus is characterized by its possessing a truncated mouth, 

 furnished with a double flagelliform or whip-shaped pro- 

 boscis, situated, as with Monas and Uvella, at the 



