Leeuwenhoek described Rotifer vulgaris in 1702, and he subsequently described Melicerta ringens and other species.
I, Simple disk of Microcodon; 2, bdelloid disk of Rotifer and of most Melicertids showing dorsal gap; 3, disk of Hydatina, with lobed ridges in the groove, bearing vibratile styles (membranelles); 4, disk of Melicerta ringens and M.
There is a dorsal interruption to the disk, in volving both trochus and cingulum and groove in this case the two halves of the disk may be developed in lobes, flower-shaped in Melicerta ringens, but often rounded and projecting like kettledrums. These give a strong impression of two crown wheels revolving in the same sense.
In Melicerta ringens and M.
- a, Stephanoceros eichornii in gelatinous tube; b, Acyclus inquietus in gelatinous tube, with eggs; c, Floscularia coronetta in gelatinous tube, with eggs; d, A psilus bucinedax, showing lateral (distal) antennae funnel of mouth hanging into enormous crop, stomach at apical end with gastric glands, anus on postero-ventral surface, large coiled kidneys at proximal end, uniting into median duct; e, Melicerta ringens in tube; f, same, proximal end enlarged, showing a pellet in the cup proximal to the paired lateral antennae; g, Melicerta janus, tube formed of faecal pellets.