222 Proceedings of the Royal Physical Society. 
XIX.—Notes on Food-Capture and Ciliation in the Ephyre of Aurelia. 
By Prof. J. F. Gemmill, M.A., M'D:, Dise-: 
(With Text-figures.) 
(Read 22nd March 1920. Received 22nd March 1920.) 
1. Foop-CAPTURE. 
IF we examine a healthy young ephyra of Awrelia in clean sea-water under 
suitable magnification, we shall probably find the gastric cavity empty or 
nearly so. Turn the ephyra mouth-upwards and leave just enough water in 
the dish to allow it to pulsate without righting itself. Now introduce some 
drops of a culture rich in marine ciliates of good size, and allow mixing. In 
many cases you will hardly have time to get the ephyra under observation 
again before some of the ciliates have been taken into the gastric cavity. 
The number increases with surprising rapidity. As a rule the ingested 
ciliates are dead and disintegrating, but some species remain active after 
ingestion for a period which is longer or shorter according to the freshness 
and vigour of the ephyra. It is interesting to note how the ciliates are 
. captured. The two lappets at the end of each ephyra arm are furnished, 
especially along their sides, with highly sensitive stinging cells capable of 
quickly extruding their long cnidotrichs. An infusorian touching a lappet 
is pierced and held by the stinging threads. Its movements usually get 
hampered by mucus or other colloid material produced, no doubt, chiefly by 
the lappet cells, but probably added to by the action of the poison on the 
prey. All the arms stop beating, or, more rarely, only the arm concerned 
ceases to beat. This arm now bends towards the manubrium and the 
manubrium bends towards the arm, while the lips stretch open widely in 
the same direction. The lappet is next slowly wiped across the lip and the 
infusorian thus detached. The latter now travels slowly down the manubrial 
canal to the stomach. I think it is carried by a central inhalant current 
which is compensatory to exhalant currents produced by ciliary action in the 
floor of the mouth angle grooves, but this may not be the whole explanation. 
It is curious to note how cleverly that part of the lappet which carries 
the infusorian is brought over the mouth. Thus if the prey is attached to 
the aboral surface, the arm and lappet curl completely round: if to the lateral 
surface, they are flexed in the necessary degree. Even the lips show fine 
adaptiveness, stretching and adjusting themselves to difficult captures. Their 
efforts, though persevering, are often fruitless, but they suggest appetite and 
desire as definitely as do the facial movements of ingenuous esurient higher 
