— 334 — 



Auf de m G r un de kleiner Tiimpel und an ihrer Ober- 

 flàche zwischen Lemnà; Ëuropa: klicin (Alt- 

 wàsser). Als Mitglied der «sapropelischen l-ebo 

 welt". 



Dasydytes bisetosum P. G. Thompson 1891. 



(Fig. 5(i.) 



Dasydytes b/sctosum P. G. Thompson 0); Nr. 58, 1801, 

 p. 100-102. 



(1) «In November, 1890, whilst searching for Rotifera, 1 came across, in 

 water from a pond near Leytonstone, Essex, some spécimens of a 

 Dasydytes which does not appear to be identical with any member of this 

 genus included in Dr. Zelixka's récent monograph, above referred to. 



Some half-dozen individuals were seen in ail, and afforded me opportunity 

 of making the following observations, and of securing a fairly accurate 

 sketcb of the animal. I propose to call this Dasydytes bisetosum. 



The body is plump and of oval outline when seen dorsally, rounded 

 posteriorly, and of course without any caudal fork ; anteriorly, the trunk 

 narrows to the neck, which latter is very distinctly marked off from the 

 head. A couple of transverse wrinkles in the skin are more or less visible, 

 crossing the neck. 



The head is large and wide, three-lobed in dorsal aspect, the latéral lobes 

 prominent like puffed cheeks; the wldth of the head is nearly twice lhat of 

 the neck, and about three-fourths that of the body at ils widest part. Both 

 head and neck are usually considerably flattened, excepting the latéral head- 

 lobes, which are somewhat globose and thicker than the central région of 

 the head. The trunk is not at ail flattened, appearing circular in optical 

 cross-section. 



The head is covered on ail its surfaces, dorsal, latéral, and ventral, wilh 

 numerous vibratile cilia, directed backwards. 



The body is furnished, on its latéral surfaces, with a few rather short, very 

 thin and délicate, somewhat appressed bristles,apparently arranged in about 

 three longitudinal rows on each side, though this is a point difficult to déter- 

 mine. I do not think any bristles occur on the dorsal surface proper. Thèse 

 setae occur also on the sides of the neck, and, in side view of the animal, are 

 seen to be directed dorsally and posteriorly ; none are nearly so long as the 

 terminal caudal bristles to be described. 



The animal's ventral surface is longitudinally furred wilh active cilia, like 

 ail the members of the order. The body is rounded behind, and has a 

 terminal projection, convexly truncate, from which are given off two long, 

 thin and délicate setae, quite one-third the total length of the animal's body 

 and head, set wide apart at their base, and carried parallel or with their tips 

 in contact. 

 It is on account of thèse two conspicuous tail-bristles, which serve by 



