140 DESCRIPTION OF {Tolygaslrica. 



mornm. Pohjtoma was described by Ehrenberg in the family Mona- 

 dina, but the subsequent discovery of the genus Spandylonomm, 

 having the same general characters, and diifering like it from the 

 other monads, led him to create this new family Sydomorina to 

 embrace the two. 



Genus Polttoma. The Partile Monads. — Mouth truncated, fur- 

 nished with a double flagelliform proboscis, situated, as with Monas 

 and Uvella, at the anterior extremity of the body ; eye and tail 

 wanting. As the young increase in size, the parent body assumes a 

 decussated or wrinkled appearance, like a miilberry, thus giving 

 signs of its approaching self-division into many sections (as the name 

 Pohjtoma denotes), or numerous individuals. It will not imbibe 

 colouring matter; but its internal organization bears the usual 

 evidences of the Polygastric nutritive system. Its only organ of 

 locomotion is the double proboscis. A large contractile vesicle, 

 sometimes observable within the creature, Ehrenberg conceives to 

 belong to the male propagative apparatus. It increases by spon- 

 taneous self-division of its body, both transversely and longitudinally, 

 thus dissolving, as it were, its berry-like cluster into many indi- 

 viduals. It was known to MiiUer and "Wrisberg. One species has 

 been recognized. 



P. uvella. {Monas uva, M.) — Colourless, of an oval or oblong 

 form, equally obtuse at both extremities. It is often abundant 

 in water, where animal matters are in solution, upon which it 

 appears to be nourished. It is generally in company with species 

 of Vibrio and Spirillum, and sometimes with Uvella uva, and 

 U. atomus, in water-butts. 



Figures 8 and 9 represent two individuals; figure 10, another 

 about to divide longitudinally ; a cluster of eight is seen at fig. 7 ; 

 and a matured one on the point of separating at figure 1 1 . Pigui'e 

 9 is magnified 800 diameters, showing the double proboscis very 

 distinctly ; and its body seems enveloped in an outer tunic (probably 

 induced by the peculiar contraction), which disappears when the 

 division is completed. Size from 1 -200th to 1 -900th. Diameter of 

 clusters 1 -380th. 



Genus Spondylomoettm. — The members of this genus are furnished 

 with adorsal ocellus ; are destitute of a tail, and in consequence o^ 



