370 DESCRIPTION OF [Rotatoria. 



and two pancreatic glands. An. ovarium exists in both 

 species, and in one of them a contractile vesicle ; nothing 

 is known of the vascular system, unless the two soft horns 

 at the brow are respiratory tubes ; a large frontal ganglion, 

 and a round red eye, indicate the system of sensation. 



626. POLYARTHRA trigla. The narrow-fingered Poly- 

 arthra. Body oval, almost square, having six setaceous 

 pinnae. It swims quickly, and often leaps, like the water 

 flea ; this last motion is produced by the fins, or finnae, the 

 former by the vibratile organs. Fig. 425 represents an 

 under side view, while the animalcule is swimming, with 

 the finnae depressed ; Jig. 400 is a dorsal view, while leap- 

 ing, or springing; and^/Tg. 401 is a side view (right). This 

 creature is infested with Colacium. Found amongst con- 

 ferva. Length l-140th. 



627. POLYARTHRA platyptera. The broad-Jingered 

 Poly art lira. Body oval, almost square, with six serrated 

 broad sword-shaped pinnae. It is represented at fig. 402. 

 Found amongst Chlamidomonas. Length 1-1 90th. 



Genus CLVIII. DIGLENA (?). The two-eyed Rotatoria 

 have two frontal eyes, and a forked foot. Excepting the 

 foot, and rotatory organ, they have no external prominent 

 organ, though some protrude the teeth in a pincer-like 

 manner. The nutritive apparatus is indicated by a mus- 

 cular oesophagal head, having single-toothed jaws; an 

 oesophagal tube, very short, except in D. lacustris ; a simple 

 conical alimentary canal in six species ; and a constricted 

 one, or stomach, in two species. In all, two pancreatic 

 glands are present, which, in D. lacustris, are long, cylin- 

 drical, and two-horned ; in the rest they are spherical. The 

 ovarium, in D. lacustris, is band-like; in the others, like 



