22 2 ROTIFER A chap. 



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 out- 

 growth of a foot in the quadrant between the mouth and am 

 and the flattening of the upper hemisphere would bring its orgai 

 on the whole into close correspondence with those of the rest 

 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. 1 



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. 2 



Fam. 5. Philodinidae : Philodina E. (Fig. 110), Rotifer Schrank, Acti?iurus 

 E., Callidi?ia 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 debris 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 



1 This second species has also been found in the Northern United States. 



2 This Order has been monographed recently by Janson in Abh. Ver. Br em. 

 Bd. xii. Beilage, 1893, p. 1. 



