OF THE HTDATINJEA. 



685 



attenuated at both ends. Usually sui'- 

 roimded by a broad gelatinous sheath, 

 either hyaline or filled with small aci- 

 cular bodies. According to Ehrenberg, 

 in this sheath vegetate threads of Hy- 

 drocrocis ; but these could not be found 

 by Leydig. Sheath wanting in young 

 specimens. Cuticle thick, soluble in 

 caustic potass. Behind the middle of 

 the body, on each side, is a small conical 

 eminence (xxxvni. 26 ft), surmoimtedby 

 a bunch of long setae. Rotary organ pe- 

 culiar, differing from Ehrenberg's repre- 

 sentation. Anterior ciliated extremity 

 small compared vnt\\ the size of the 

 animal ; ventral portion (fig. 26 c7) pro- 

 longed in the form of a half canal or 

 gTOOve, constituting a kind of under lip. 

 At the base of this is the mouth, com- 

 municating with the maxillary bulb and 

 oesophagus, and opening into a stomach 

 with walls composed of large cells (fig. 

 26/), beyond which is a restriction 

 separating it from the rectimi (fig. 20) g). 

 Three sac-like organs (fig. 26 t, c) on the 

 hinder border of the brain (fig. 26 k) : 

 the centre one composed of clear vesicles 

 (fig. 26 c), the outer t^^o apparently 

 sometimes continuous ^\dth the cerebral 

 ganglion. They are granular, nucleated, 

 and apparent Avith some inorganic mat- 

 ter, which is white by reflected and dark 

 by transmitted light. Ovary (fig. 26 o) 

 transversal ; Perty saw only winter ova 

 in it. (xxx^Ti. 25 exhibits'^a small por- 

 tion of the ovary in which an ovum is 

 forming, — a being the germinal spot, h a 

 clear space sm-roimding it, and c the 

 yelk-suDstance. xxxvni. 11. represents 

 a small portion of the water-vascular 

 c^nal with its tags, and fig. 12 the ter- 

 mination of a tag with its contained 

 ciliuni.) 



N. hrachyota. — Small, slightly attenu- 

 ated towards the ends ; no tail, auricles 

 very small ; it has two dark spots near 

 the' eye ; foot forked. 1-120". 



N. Phurotrocha. — Slender, cylindrical, 

 not auricled : foot with very short toes ; 



eye obscure, ovate, large ; jaw ■v^•ith one 

 tooth. 1-144". Berlin. Has the form 

 of Pleurotrocha. 



N. vermicidaris (Duj.). — Vermiform, 

 very contractile ; of variable form, \^^th 

 a kidney-shaped red speck (xxxviii. 33), 

 in which is partly imbedded a white 

 transparent globide. 1-118". Found in 

 the Seine. 



N. tardigrada (Leydig) would be re- 

 ferable to the genus Lindia (Duj.), had 

 not its author made the absence of cilia 

 from the head a generic character. Fi- 

 gure vermiform, rounded in front, pro- 

 longed behind into a short biuncinate 

 foot. Mouth a long fissm-e on the under 

 side of the head, which is clothed with 

 short and delicate cilia, the only part of 

 the head so fiuiiished. MaxiUary bulb 

 capable of being protruded. Dental ap- 

 paratus recalling to mind that oi Echinus. 

 (Esophagus long, resembling that of N. 

 centrura. Stomach long, yeUow, with- 

 out cilia on the free surfaces of its 

 parietal cells. Intestine short and clear, 

 opening at the base of the foot on the 

 abdominal surface. Contractile sac vi- 

 sible, giving off traces of two water- 

 canals, but without vibratile tags. Above 

 the maxillary bulb the " sacculus cere- 

 bralis " of Ehrenberg, white by reflected 

 and black by transmitted light, and 

 soluble in liquor potasses. 



N. roseola (Perty). — Body of a pale 

 rosy red, elongated, rounded in front. 

 Rotary organ forming a cylindrical pro- 

 cess on each side of the head. Cohn 

 suggests that the animal may be identical 

 with his Li)idia toridosa. 



N. onisciformis (Perty). — Body broad 

 like an Oniscus, with a roimd lappet on 

 each side of the head. Jaws strong, 

 many-toothed; tail flat, rather long. 

 Entire anterior extremity capable of 

 being retracted. An ear-like lappet on 

 each side of the head, between which 

 are seen the vibratile cilia. No alimen- 

 tary canal seen beyond the maxillary 

 bulb. Amongst Confervae and Charse. 



Genus SYNCH^TA (XXXIII. 422).— Eye single, cei-^dcal ; rotary organ 

 of six to ten lobes, and armed with from two to four styles ; foot fui'cate. 

 The strong styles, or bristles, are situated between the clusters of cilia, and 

 probably act as tactile organs ; the body is very short, broad anteriorly, and 

 tapers to a point posteriorly, or is conical. Internal longitudinal muscles 

 exist in all the species ; those of the foot are seen in three species : the oeso- 

 phageal head is large, with single -toothed jaws ; but in two species only is the 

 whole che'wing apparatus distinctly seen. The thin oesophagais is long in two 

 species, short in the rest; it leads to a simple, wide, conical alimentary 

 canal, which has two roundish, or, in one species, conical pancreatic glands. 



