Hydatinaea.] THE INFUSORIA. 373 



Genus CLIX. Triarthra. The three-bearded Rota- 

 toria possess two frontal eyes ; a simple styliform foot, 

 and beardj or breast fins. Beside the vibratile organs, 

 internal band-like muscles are observed, and two bristles, 

 or fins, which assist in leaping ; these remind us of Poly- 

 arthra. The nutritive apparatus consists of an oesophagal 

 head, having four muscles, and two double-toothed jaws, 

 as in Rotifer ; an oesophagal tube, long in one species, 

 short in the other ; and a simple, conical, or constricted 

 alimentary canal, with two spherical glands. Both ova- 

 rium and contractile vesicles are seen ; the eggs, when 

 expelled, remain attached by threads. A vascular system 

 is unknown — the nervous is indicated by the two red eyes, 

 placed upon ganglia. Both species often produce a 

 milky turbid appearance in the water, when developed in 

 masses. 



636. Triarthra loiigiseta (Trichoda, M.) TTie long- 

 bearded Triarthra. — Eyes distant, the cirri, or beards, and 

 the foot, are nearly three times the length of the body. 

 This species is distinguished from the following one by the 

 greater length of cirri, by larger eyes, which are further 

 removed from each other ; by a distinct stomach, with a 

 constriction separating it from the long portion of the 

 alimentary canal ; and, lastly, by its long oesof)hagal tube. 

 It is readily distinguished by its leaping movement whilst 

 swimming. Fig. 408 represents one of these creatures 

 emerging from the egg, the cirri or styles being, as yet, 

 soft : Jig. 407 is a back view of a young specimen ; it shews 

 the great separation of the eyes and the styles, in the posi- 

 tion they take when the animalcule is swimming; and^'^. 

 406 is a side (right) view of a full-grown specimen ; the 



