_Trochosphaera_ (Fig. 118, D) is remarkable for its peculiar {222}spherical shape, the absence of a foot, the limitation of the viscera to the lower hemisphere, and the dorsal position of the ovary. But a reference to the figure will show that the outgrowth of a foot in the quadrant between the mouth and anus and the flattening of the upper hemisphere would bring its organs on the whole into close correspondence with those of the rest of the Order. It is recorded from South China, the Philippines, and North-East Australia, and has only been seen by Semper, the founder of the genus, and by Thorpe, who saw the male of the first species, and described a second.[270] ORDER III. BDELLOIDA.—Females creeping like a leech, as well as swimming (males unknown), susceptible of desiccation and revival ("anabiotic"). Body telescopic at both ends. Disc (except in _Adineta_) chiefly composed of two dorsal lobes like kettle-drums, wholly retractile; a dorsal proboscis or trunk-like prolongation of the body ends in a ciliated, sensory, and adhesive cup used in crawling, and overhung by a pair of membranous flaps. Trophi ramate; brain with a ventral ganglion, forming a complete ring. Eyes, two on the proboscis or brain, or absent. Bladder a mere dilatation of the rectum. Foot often possessing blind spurs, as well as two or three retractile perforated toes, or forming a terminal disc perforated by numerous pores of the cement glands, rarely ciliated.[271] Fam. 5. Philodinidae: _Philodina_ E. (Fig. 110), _Rotifer_ Schrank, _Actinurus_ E., _Callidina_ E. (Fig. 109), _Adineta_ H. This group is remarkable for the great resisting powers of its members to drought and to heat and cold when dried, a fact which may explain the absence of males, though Janson records the occurrence of winter eggs in four species of _Callidina_ and in _Adineta vaga_. The body is often strongly pigmented; red in _Philodina roseola_, _Callidina scarlatina_, and _C. russeola_, yellow in _P. citrina_, _Rotifer citrinus_, and _Discopus synaptae_. Most of the species are dust- or moss-dwellers; some, such as _Rotifer vulgaris_, are equally common in organic débris in infusions, pools, and ditches. _Discopus_ adheres to the skin of the Holothurian _Synapta_. ORDER IV. ASPLANCHNACEAE.—Females ovoid, footless except in _Asplanchnopus_. Disc often bearing a pair of antennae; circular, often prolonged at the margin into two rounded lobes, interrupted {223}dorsally, depressed at the ventral side into a deep ventral funnel. Trophi incudate (virgate in _Ascomorpha_), mastax enlarged dorsally into a wide crop; stomach large, blind. Kidneys large, with a "recurrent duct" and numerous tags; bladder large. Brain large, with a median eye, and frequently paired smaller eyes at the base of the marginal processes of the disc; anterior antennae paired, relatively far back on dorsal surface. Males (Fig. 107, 5) relatively large, frequently found.