ACALEPH.E. 



67 



corrugated, as it were, into minute radiating plicae, which seem 

 to contract more energetically than the other portions, and re- 

 semble a rudimentary developement of muscular fibre. 



(95.) Ciliograda. In the Ciliograde acalephse, the organs of 

 motion are of a very different description, consisting of narrow 

 bands of vibratile cilia variously disposed upon the surface of 

 the body, which in their motions and office resemble those of 

 the polygastric animalcules. 



In the globular forms of Beroe (fig. 22) the cilia are generally 



arranged in eight longitudinal bands, and appear to be attached to 

 subjacent arches of a firmer consistence than the rest of the body. 

 They are generally quite naked, but in Pandora are lodged 

 between folds of the skin, which will close over and completely 

 conceal them ; their motion is extremely rapid, and sometimes 

 only recognisable by the currents which they produce, or the 

 iridescent hues which play along the arches. The ciliary action 

 seems to be perfectly under the control of the animal, as it can 

 retard or stop their motions at pleasure, sometimes arresting the 

 play of one, two or more rows, whilst the rest continue in rapid 

 vibration, and thus changing its course, or causing its body to 

 revolve in any direction. In some of the Ciliograda, the loco- 

 motive cilia are of considerable size ; and in Cydippe pileus their 

 structure has been particularly examined by Dr. Grant.* In this 

 animal eacli cilium, instead of being a simple filament, seems to 

 be made up of several, arranged side by side, so as to form a flat 

 membranous organ, not unlike the fin of a fish (fig. 22 ; 3, 4) : 

 the individual filaments appear tubular when viewed under a 

 powerful magnifier, and are slightly curved backwards, so that 



* Transact. Zoolog. Society of London, vol. i. 



