298 Proceedings of Royal Society of Edinburgh. [sess. 
later. As a rule, only a few young are extruded at one time, and 
generally early in the morning, and one individual may repeat this 
operation every morning for several weeks. The young, the 
majority of which when extruded already possess the first two 
cycles of tentacles ( i.e . twelve tentacles), are not expelled with 
violence, hut gently, and usually lie for a time, with their tentacles 
retracted, on the disc of the parent. They are dispersed in a 
manner which is no doubt very useful and effective in a tidal pool 
on the sea-shore. At or soon after extrusion the basal portion 
of each young anemone is much swollen, owing to the presence of 
a considerable amount of fluid in the coelenteron, so that the pedal 
disc becomes strongly convex. This is probably due to the fact 
that the tentacles being retracted and the mouth closed, the 
products of metabolism are unable to escape. In addition to their 
mere accumulation, the soluble products exert some osmotic action 
which causes sea-water to diffuse through the thin body-wall into 
the coelenteron, thus strongly inflating the basal portion of the 
young animal. Owing to this basal inflation and the retraction 
of the oral end the young anemone has an almost globular shape, 
so that the slightest current in the water causes it to roll off the 
oral disc of its parent, and often carries it some distance before it 
sinks to the bottom, as its specific gravity is not much greater than 
that of sea-water. As soon as the young anemone finds the 
bottom of the vessel it becomes orientated in the proper direction 
and fixed by the pedal disc, apparently possessing already that well- 
marked polarity which is characteristic even of pieces of adult 
anemones which include a portion of the pedal disc (see A. P. 
Hazen, Arch. f. Entwiclcelungsmechanih d. Org ., Bd. 14, 1902, pp. 
592-599, and Bd. 16, 1903, pp. 365-376, Sagartia lucice). We 
have occasionally seen adult specimens of Actinia mesembryan- 
themum assume this globular and buoyant form, the pedal disc 
becoming free from its attachment, the basal part of the animal 
swollen and the oral disc retracted. Both S. troglodytes and A . 
mesembryanthemum are frequently found in this condition at birth, 
but adult specimens of the former rarely adopt it, though a case is 
mentioned by Gosse (1860, p. 95). S. troglodytes seems to rarely 
change its station when once settled in a cavity which is to its 
liking. 
