200 



ROTIFERA 



rarely, and the females are usually viviparous, or carry about 

 the eggs till they are hatched ; while, owing to the rarity oi 

 the males, parthenogenesis is habitual. Fission and budding are 

 alike unknown. The fertilised eggs are of the kind termed 

 " winter " or " resting " eggs, and resist conditions adverse to life. 

 The Eotifera are of cosmopolitan distribution ; most of the 

 species inhabit fresh water, whilst some are brackish, and a few are 

 marine; 84 genera and about 700 species have been described. 



Fig. 107. Male Rotifers. (After Hudson. 1 ) 1, Floscularia campanulata ; 2, Laeim 

 laria socialis ; 3, Notops brachionus ; 4, Synchaeta tremula; 5, Asplanchna 

 bornii ; 6, Brachionus urceolaris ; 7, Salpina mucronata ; 8, Pedalion mirum. 



External Features. 2 The body is divided into three regions 



(1) the head, ending in the disc, which bears the ciliary wreath 



(2) the trunk, containing the viscera; (3) the foot, which onkj 

 contains muscles, nerves, and cement-glands. The general fori 

 of the body varies greatly : it is spherical in Trochosphaera, 

 ovoid in Asplanchnidae, conical in Scirtopoda, Triarthridae, and 

 Synchaeta; moderately elongated in the majority of the Ploima, 

 among which some forms are very flat, like Pterodina, Metopidia, 

 and Brachionus ; shortly elongated and cylindrical in Hydatina 

 (Fig. 106), Notommatidae, and many others. In Taphrocampa 

 it is cylindrical and segmented, while the segments are tele- 



1 Quart. Journ. Micr. Soc. (n.s.) vol. xxiv. 1884, p. 352. 



2 The definition of the Orders and systematic position of the genera and species 

 referred to under this head will be found in a following section (pp. 220 # f.). 



