OF THE HYDATIN^A. 679 



Dujardin would include in the genus ffydatina several Eotatoria distributed 

 by Elii'enberg among other genera. He says : " Notrdthstanding the presence 

 of a red eye-speck, we must consider as Hydatinae — 1. Notommata tuba ; 

 2. N. brachionus ; 3. N. trijpus ; 4. N. davxdata,'^ and, though doubtfully, N. 

 saccigera, for this species in form resembles a true Furcularia. "■ The Syn- 

 chcetce (Ehr.), characteiized by theii' stiff setae or styles, are true Hydatinae 

 from their conical or campanulate form, if theii' jaws are really pectinated; 



but if not, they will constitute a genus apart The Distemma maximum, 



represented by Ehrenberg with pectinated jaws, and placed as doubtful by 

 him in the genus Distemma, characterized by a double eye-speck, appears to 

 be a tnie Hydatina.'^^ 



Genus PLEUEOTROCHA (XXXII. 395, 396).— These have no eyes, but 

 possess a single tooth in each jaw, and a furcate foot. The rotary organ con- 

 sists, not of a simple wreath of cilia, but of cilia distributed in bundles near 

 each other, the bundles being planted in muscular cases. In P. gibha there are 

 two muscles for moving the foot ; and in aU the species the globular oesophageal 

 head has four, acting upon two single-toothed jaws (fig. 396) ; oesophagus 

 short ; alimentary canal simple, conical, having anteriorly two spherical glands. 

 The anus is at the base of the foot, upon the dorsal surface. The ovary is 

 globular. In P. leptura a contractile vesicle is seen. Organs of sensation 

 are not satisfactorily known, and the nervous loop in the neck of the ffydatina 

 appears wanting. This genus is not admitted by Dujardin. 



PLEunoTROCHA g/bbci. — Truncated i animalcule is very active and powerfid. 

 anteriorly, enlarging from the front to- | Upon Ceratophyllum. 1-144". 

 wards the base of the foot, where it is i F.leptura. — Body turgid in centi-e, front 

 suddenly attenuated, the toes, or claws, 

 short and turgid ; near the mouth is a 

 beak-like projection, forming an under 

 lip. XXXII. .395 is a right side view; 

 396 the teeth and oesophageal head dis- 

 sected out. Found with ffydatina bra- 

 chydactyla. 1-216". 



P. constricta. — Elongated, conical, 

 head separated by a stricture ; front ob- 

 lique; toes straight and slender. This 



oblique ; foot slender ; toes thin, shghtly 

 curved. iVmongst Conferv^ae. 1-144". 



P. renalis (Ehr.). — Elongate, slightly 

 constricted in front, toes short, frontal 

 portion rather oblique, ti'uncate, pan- 

 creatic glands kidney-shaped (reniform). 

 1-240". Berlin. 



P. truncata (Gosse). — Subcylindrical ; 

 truncate behind above the foot ; toes 

 short, straight, slender. 1-175". 



Genus FUECULAEIA (XXXIII. 397, 398).— Frontal eye single; foot 

 forked. Eotary organ compound. Longitudinal muscles exist in F. gibba, 

 and foot-muscles in three species. The oesophagus is very short, its head has 

 two jaws, single-toothed (Monogomphia) in two species, but not in the others ; 

 alimentary canal simple (Coelogastrica), conical, with two ear-like glands ; 

 ovary distinct, except in F. gibba, which has only a contractile vesicle. 

 Vessels, respiratoiy tubes, gills, &c., are not recognizable. The eye in 

 F. Reinhardtii is placed upon a brain-like mass. 



Dujardin has the following remarks on the genus Furcidaria : — '^ The 

 genus Furcidaria, one of the most numerous, undoubtedly requii^es to be 

 divided after new observations, but not according to the number and dis- 

 position of the red points, as has been done by Ehrenberg. This author has 

 indeed distributed some Systolides, which appear to us to have the closest 

 relations in form and mode of hving, into eight genera " (viz. Pleurotrocha, 

 Furcularia, Notommata, Scaridium, Dighna, Distemma, Eosplio^^us, and 

 Theorus) ; ^' but many of these are purely nominal, and require a rigid 

 revision. 



'' The following are the principal species to be classed with certainty among 



