452 INFUSORIA. 



the first. It most commonly terminates posteriorly in a tail that is 

 variously constructed, and anteriorly it bears a singular organ, va- 

 riously lobate, with denticulated edges, and of which the denticula- 

 tions vibrate successively in such a manner as to give the organ itself 

 the appearance of one or more dentated and revolving wheels. One 

 or two prominences on the neck have even appeared to some ob- 

 servers to be furnished with eyes. This revolving organ does not 

 serve to direct their aliment to the mouth ; it may be supposed to 

 have some connection with the function of respiration *. In 



FuRCULARiA^ Lam., 



The body is unarmed ; the tail is composed of articulations which 

 enter one into the other, and is terminated by two threads. 



It is on one of these — the Furcularia or Rotifere des toils — that 

 Spallanzani performed his famous experiments. Covered with dust 

 in the spouts on the roofs of houses, it becomes desiccated, and after 

 remaining in that state for several weeks re-acquires life and motion 

 on being humected with a little water. 



Tlje Trichocerc^, Lam., appear to me to differ from the Furcu- 

 laria only in the diminished development of their vibratile organs f. 

 The 



Vaginicola, Lam., 



Seem to be Trichocercae with a diaphanous envelope ; but we may 

 be allowed to fear there has been some optical illusion X. 



TuBicoLARiA, Lam. 



The Tubicolarife only differ from the Furcularise, by secreting them- 

 selves in little tubes, Avhich they construct of foreign molecules, but 

 which do not form any jwrtiun of their body, like those of the Coral- 

 liferi (polypiers). Their rotatory organ however shows itself out of 

 the tube, nearly in the manner of the head of Polypi. 



There is a species in France common on the Confervae of the 

 marshes — Vorlicella tetrapctala, Blumenb. ; Dutrochet, Ann. 

 du Mus., XIX, xviii, I — 10 — whose rotatory organ is divided 

 into four lobes. 



Brachionus, ISlulL 



The Brachioni, with rotatory organs and a tail nearly similar to 

 those of the Furculariae, have a sort of membranous or squamous 

 shield, which covers their back like that of certain Monoculi. 



* For the organizatioa of these anim.ils, see the Memoir of M. Dutrochet, Aun. 

 du Mus. XIX, p. 355. 



t Trichoda paxiUum, Miill.. XXIX, 9—12; Encyc., XV, 19, 20 •,—Trich longi- 

 cuuda, Mull., XXXI, 10. 



X Trick, innuta; — Tr. ingenita; — Tr. inquilina, Miill. 



