144 THE ROTATORIA. "§> 134. 



is quite remarkable with those species whose single or double disc is not 

 crenulate, but entire. *^^ With those whose organs are more numerous, but 

 smaller, this appearance is not observed.'^* 



With Floscidaria, and Stepkanoceros, the rotatory organs have quite a 

 different form. With the first, there are five or six button-like processes 

 about the mouth, covered with very long bristles ; these bristles produce 

 usually but very feeble motions, and rarely give rise to vortexes. Eut S^e- 

 phanoceros reminds one much of the Bryozoa, for its rotatory apparatus con- 

 sists of five tentacle-like processes covered with vibratile cilia ^'^^ The rota- 

 tory organs differ, moreover, from the ordinary vibratile cilia of epithelium, 

 in being under the animal's control, — that is, moved or kept at rest, at 

 will.'^^ 



CHAPTEKS III. AND IV. 



NERVOUS SYSTEM AND OEGANS OF SENSE. 



§ 134. 



Notwithstanding the transparency of the Kotatoria, and the distinctness 

 with which their organs are separated from each other, yet their nervous 

 system has not yet been made out with certainty, for their bodies are so small 

 that their peripheric nerves elude the microscope, and their principal nerves 

 and ganglia cannot be distinguished from the muscular fasciculi, the liga- 

 ments, and the contractile parenchyma of the body. 



It appears certain, however, that in all, there is, as a nervous centre, a 

 group of cervical ganglia, from which pass off threads in various direc- 

 tions.^" 



1 Conochilus, Philodina, and Actinurus. uliform body found upon most Rotatoria, and in 



2 Hydatina, Notommata, Synchaeta, and Dig- the neck of Hydatina senta, and Notommata col- 

 lena. laris (Abhandl. d. Berl. Akad. 1830, p. 52, Taf. 



3 See Ehrenberg, Die Infusionsthierchen, Taf. VIII. 1833, p. 189, Taf. IX., and, Die Infusionsthier- 

 XLV. chen, p. 386, &c.). Besides this ganglion, he has 



4 According to £Arpn6frg-, there are, at the base mentioned with Hydatina, Synchaeta, and Dig- 

 of each cilium of the rotatory organs, many striated lena, many others scattered tlirough the anterior 

 muscles, which, acting antagonistically, produce the part of the body, and connecting with the cerebral 

 motion (Abhandl. d. Berl. Akad. 1831, p. 34). one by nervous filaments. Likewise, with Enter- 

 But neither Dujardin (Infusoires, loc. cit. p. oplea, Hydatina, Notommata, and Diglena, he 



579), nor Rymer Jones (Compar. Anat. &c. p. has regarded as a nervous loop, the two filaments 



120), has been able to perceive this apparatus, which pass off from the cerebral ganglion, and go to 



The contractile parenchyma on which the virbra- the cervical respiratory orifice. Finally, he refers 



tile discs are situated, appears to be destined only to the sensitive system, a white sacculus, single or 



for the protrusion and retraction of the rotatory double, and situated behind the cerebral ganglion, 



organs.* with Ifotommata, Diglena, and Theorus (Die 



1 Ehrenberg, to whom we are indebted for our Infusionsthierchen, p. 425). Grant^s description of 



chief information upon the nervous system of these the nervous system of the Hydatina, as being 



animals, first took for a cerebral gangUon the gland- composed of many ganglia and a ventral cord, 



*[§ 133, note 4.] Doti'e (Aim. of Nat. Hist. 1848) long and filiform, of uniform thickness, and not 



speaks of two kinds of ciUa with F/osCM^arja; "one Vibratile under ordinary circumstances." They are 



of the usual short vibratile kind, covering the inte- slowly moved, being spread out by the contractile 



rior of the alimentary tube ; the other extremely substance of the lobes of the rotatory organ. — Ed. 



