G30 DESCRIPTION OF \Rolaioria. 



of a red eye speck, we must consider ^^Hydatlnae, — 1. Notommata 

 tuba; 2. N. brachionus ; 3. N. Mpus ; N. c^awM^a^a," and, though 

 doubtfully, N. saccigera, for this species in form resembles a true 

 Furcularia. "The Synehoetoe (Ehr.) characterized by their stiff 

 setae or styles, are true Hydatina from their conical or campanulate 

 form, if their jaws are really pectinated, but if not they will con- 

 stitute a genus apart." . . . "l^\\e Bistemna maximum, xe^v&iexiteA. 

 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 true Hydatina." 



Genus Pleurotrocha. — The awl-shaped tooth Rotatoria have no 

 eyes, but possess a single tooth in each jaw, and a furcate foot. The 

 rotatory organ consists, not of a simple wreath of cilia, but of cilia 

 distributed in bundles near each other, the bundles being placed in 

 muscular cases. In P. gibba there are two muscles for moving 

 the foot, and in all the species the oesophageal head has four. 

 This head is globular; it has two single-toothed jaws (fig. 396) ; 

 these, and the short oesophagus, the simple conical alimentary 

 canal, having anteriorly two spherical pancreatic glands, con- 

 stitute the nutritive apparatus. The posterior opening of the 

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

 propagative system consists of a globular ovarium. In P. leptm-a 

 a contractile vesicle is seen. Organs of sensation are not satis- 

 factorily known, and the nervous loop in the neck of the Hydatina 

 appears wanting in this genus. This genus is not admitted by 

 Dujardin. 



P. gibba. — Body truncated anteriorly, enlarging from the front 

 towards the base of the foot, where it is suddenly attenuated, the 

 toes, or claws, short and turgid ; near the mouth is a beak-like 

 projection, forming an under lip. Fig. 395 is a right side view, 

 and fig. 396 the teeth and oesophageal head dissected out. Found 

 with Hydatina brachydactyla. Length 1-2 1 6th. 



P. constricta. — Body elongated, conical, and separated from the 

 head by a stricture ; front oblique, toes straight and slender. This 

 animalcule is very active and powerful. Found upon Ceratophyllum. 

 Length l-144th. 



P. leptura. — Body turgid in the centre, front oblique, foot 



