232 TROCHELMINTHES 



rotifers and their eggs can withstand desiccation many years when taken 

 from the water and are often blown great distances by the wind or carried 

 on the feet of birds. The food of most forms consists of minute plants 

 and animals, but a few species are parasitic. 



History.— Rotiters have been known since the time of Leeuwenhoek, 

 who discovered them in 1703. 0. F. Miiller in 1786 gave those known at 

 his time binominal names, classifying them with the Infusoria. Ehren- 

 berg, in his epoch-making work on Infusoria published in 1838, described 

 great numbers of rotifers and laid the foundation of the present classifi- 

 cation. Wiegmann in 1832 had, however, already removed them from the 

 Infusoria and placed them among the worms. The monograph of Hudson 

 and Gosse contains the modern classification of the group. 



About 850 species of Rotifera are known, of which about 250 occur 

 in this country. They are grouped in 3 orders. 



Key to the orders of Rotifera: 



tti Sessile or colonial and usually tubicolous (except Trochosphwra) . 



1. Rhizota 



flo Free-swimming ; not tubicolous and non-colonial rotifers. 



6i Rotifers which creep like a leech, but can also swim 2. Bdelloida 



&2 Rotifers which do not creep but swim 3. Ploima 



Order 1. RHIZOTA. 



Usually sessile rotifers living in tubes composed of a transparent 

 secretion or of fecal or other substances; some forms are colonial and a 

 few are free-swimming: 3 families. 



Key to the families of Rhizota here described : 



Oj Corona with prominent non-vibratile cilia usually on lobes ; vibratile cilia 



very small 1. Flosculariidae 



02 Corona without non-vibratile cilia ; colonial or not 2. Melicertidae 



Family 1. FLOSCULARIIDAE.* 



Solitary, sessile, or free-swimming rotifers living in a transparent 

 tube; corona lobed in most cases and bearing groups of long, often non- 

 vibratile cilia; vibratile cilia few, about the mouth: 3 genera. 



Key to the genera of Flosculariidae here described: 



«! Lobes of corona knobbed or blunt, or absent 1. Floscularia 



«2 Lobes long and pointed 2. Stepiianoceros 



1. FLOSCTTLARlAt Oken. Body in a transparent tube; corona with 



3 to 5 lobes, or not lobed, and bearing long non-vibratile cilia ; the young 

 of all and the adults of certain species free-swimming: about 30 species. 



* See "On the Morphology of the Rotatorian Family Flosculariidae," by T. H. 

 Montgoinpry, Jr., Proc. Acad. Nat. Sci., Phila., 190:{, p. :>0.'>. 



t See "On Floscularia Conklini Nov. Spec, with a Key for tbo Identification of 

 the Known Species of the Genus," by T. H. Montgomery, Jr., Biol. Bull., Vol. 5, 

 p. 233, 1903. 



