Food-Capture and Ciliation in Ephyre of Aurelia. 225 
detached will move slowly aboralwards by ciliary action, and 
rotate counter clockwise as viewed from the aboral end. 
. Subumbrellar surface of arms—centrifugally outwards. 
Subumobrellar surface of disc—centrifugally outwards on a marginal zone 
of about a quarter radius breadth; centripetally on remainder. 
Subumbrellar surface of manubrium—towards the mouth opening. 
. Internal surfaces.—Roof of gastric cavity and of all radiating canals— 
centrifugally outwards. 
Floor of gastric cavity and of all radiating canals—centripetally 
inwards. 
Manubrial canal—ciliation absent or ill-defined, except in floor of 
i) 
Os 
radial grooves where it is weakly exhalant. 
Gastric filaments—from base to tip of each filament. 
The usefulness of the ciliation throughout the internal cavities is obvious. 
That of the external ciliation in relation to feeding is referred to on p. 224. 
Widmark has described the ciliation in the Awrelia itself. Among 
characteristics he notes that there is well-marked centripetal movement of 
fluids along both the perradial and interradial canals, and centrifugal 
movement along all the adradials, while the perradial grooves of the 
manubrial cavity exhibit strong ciliary action towards the mouth opening. 
The medusa of Melicertidium exhibits much the same internal ciliary 
activities as the Aurelia ephyra, but externally ciliation is absent from the 
exumbrellar and considerable portions of the subumbrellar surfaces. 
References to recent papers on ciliation in other marine invertebrates are 
given below. | 
1. CarteGREN, O. Biol. Centralbl., xxv., 1905, pp. 308-322 (Actinians, 
Madreporarians). | 
2. Orton, J. H. Journ. Mar. Biol. Ass. U.K., ix., 1912, pp. 144-178 
(Ascidians, Molluscs): zbid., x., 1913, pp. 19-49 (Amphioxus, Ascidians, 
Molluscs). : 
3. WipmarkK, HE. M. PP. Zs. Allg. Phys. Jena, xv., 1913, pp. 33-48 (Aurelia). 
4, Gemuity, J. F. Proc. Zool. Soc. Lond., 1915, pp. 1-19 (Starfish) ; zbzd., 
1919, pp. 263-265 (Ctenophore) ; zbid., pp. 459-461 (Lepto-medusa). 
(Issued separately, 6th May 1921.) 
