ROTATORIA. 



[ 671 ] 



RUCKER1A, 



situated usually in the cervical region (PI. I 

 43. fig. 3 ; PL 44. fig. 17), denominated the i 

 calcar or respiratory tube, and terminated 

 by a retractile tuft of non-vibratile cilia 

 (fig. 5 ). They have no relation, how- 

 ever, with this, which corresponds to an 

 antenna. Huxley proved that they are 

 part of a water-system. 



Beneath the integument of the Rotato- 

 ria, a kind of irregular circulation, varying 

 with the motions of the body, or a simple 

 molecular movement of minute granules, has 

 been noticed. These granules are probably 

 situated in the abdominal cavity j in which 

 also sarcodic globules, sometimes free, at 

 others connected by filaments, have been 

 observed. 



Reproduction. -The Rotatoria are propa- 

 gated by means of sexual organs, and are 

 unisexual. The female organs consist of 

 one or two longer or shorter ovarian sacs or 

 ovaries, situated towards the posterior end 

 of the body in the abdominal cavity, the 

 oviduct terminating in the cloaca, or at a 

 distinct vulva. The ova are of an oval 

 form, and are sometimes smooth externally 

 and soft. The winter-ova are larger an'd 

 darker than those hatched during the sum- 

 mer, and the outer coat is thick and hairy 

 or tubercular. The winter-ova which re- 

 main so long attached to the posterior part 

 of the body are probably gemmse ; they 

 sometimes remain adherent to the cloaca 

 for a time, and in a few instances they are 

 hatched within the ovary. 



The testis is situated at the posterior 

 part of the body, and consists of a wedge- 

 shaped body, with a muscular duct opening 

 externally. 



Many of the Rotatoria are remarkably 

 tenacious of life ; and some of them are 

 stated to have revived after having been 

 kept dry for several years. 



Perfect desiccation destroys the Rotifers, 

 but they will last a long time with a very 

 slight amount of moisture. 



The families of the Rotatoria are thus 

 distinguished : 



Ciliated margin of rotatory disk simple or continuous. 

 Margin entire. Holotrocha. 



Carapace absent Ichthydina. 



Carapace present CEcistina (?). 



Margin undulate or excised. Schizotrocha. 



Carapace absent Megalotrochsea. 



Carapace present Floscularisea. 



Rotatory disk divided or multiple. 



Divided into several parts. Polytrocha. 



Carapace absent H jdatinaca . 



Carapace present Euchlanidota. 



Divided into two parts. Zygotrocha. 



Carapace absent Philodinaea. 



Carapace present Brachionaea. 



See ALBERTINA. 



They are found wherever water exists, 

 provided it be not in a state of putrefaction, 

 thus in pools, on moist earth, mosses, in 

 gutters, &c., and even in the cells of mosses 

 and algae. 



BEBL. Ehr. Inf. j Dujard. Inf. ; Siebold, 

 Vergl An. ; Dalrymple, Phil. Tr. 1849, 331 ; 

 Huxley, Micr. Trans. 1852, i. 1 ; William- 

 son, Micr. Jn. i. 1 j Cohn, Siebold und Kol- 

 liker's Zeitsch. vii. 431 ; Gosse, Tr. Micr. 

 Soc. iii. ; id. Ann. N. H. 1851, viii. 198 

 (several new genera and species) j and 1850, 

 xviii. 333; Pritchard, Inf. ; Schmarda, Neue 

 Rotatoria, 1861 ; Mecznikow, Sieb. und Koll. 

 Zts. 1865 ; Qu. Mic. Jn. 1666, 34 & 240 j 

 Claparede, An. N. H. 1868, i. 309 ; Schloch, 

 Rdderthiere, 1869 j Cubitt, M. M. Jn. vi. 

 168, viii. 5 ; Hudson, M. M. Jn. xiii. 45 j 

 Pascoe, Zool. 



ROT'IEER, Guv. A genus of Rotatoria, 

 of the family Philodineea. 



Char. Eyes two, situated upon the pro- 

 boscis ; foot furnished with lateral horn- 

 like processes, and with two terminal toes, 

 giving its end a bifurcate appearance j fresh- 

 water, 



It. vulyaris (PI. 44. fig. 23). Body fusi- 

 form, white, gradually attenuated towards 

 the foot-, length 1-48 to 1-24". 



This is one of the commonest of the 

 Rotatoria, and has long been known as a 

 favourite microscopic object under the po- 

 pular name of the wheel-animalcule. The 

 anterior and upper part of the body termi- 

 nates in a proboscis, ciliated at the end, and 

 upon which the eyes are placed ; the two 

 rounded lobes of the rotatory organ are 

 placed laterally. Behind, and at the root 

 of the proboscis, is the calcar. 



In R. citrinus, the middle of the body is 

 yellowish, the horns of the foot long, and 

 the eyes round. In R. macrurus, the body 

 is suddenly narrowed into a long foot. In 

 R. tardus the body is gradually attenuated, 

 but somewhat deeply constricted into seg- 

 ments. 



BIBL. Ehr. Infus. 484 ; Pritchard, Inf. ; 

 Grenadier, M. Mic. Jn. 1870, 44. 



ROTIF'ERA. See ROTATORIA. 



RUBEFAOTION OF WATER. See 

 WATER. 



RUCKE'RIA. A genus of Composite. 

 The pericarp possesses HAIRS of an inter- 

 esting structure. 



