138 MARINE INVERTEBRATES 
the end of July they are fully developed, and begin to discharge their eggs, 
which go into the folds around the mouth and remain there until they at- 
tain the planulastage. After the spawning 
period the meduse, reduced in strength, are 
unable to resist the storms of the autumn, 
and many of them are cast ashore; many 
others, in a more or less wasted condition, 
float near the surface, but the body is less 
transparent, its tissues are thickened, its 
tentacles gone, and general dissolution has 
commenced. In this condition the medusze 
are frequently capsized by the air which ac- 
cumulates in the empty egg-cavities, and, 
floating helplessly on the surface, are at- 
tacked and destroyed by swarms of small 
crustaceans; thus their cycle of life is ter- 
minated. It has been suggested that the Strobila of Aurelia flavidula. 
destruction of the mothers, by being cast 
upon the beaches in the autumnal gales, is a provision to set free the 
planule in a position favorable to their existence ; for when liberated 
Cyanea arctica, greatly reduced in size. 
they fasten upon the rocks and sea- 
weeds of the shore, where, during the 
winter months, they develop into stro- 
bile, which in turn free their saucer- 
like disks early in April. 
GENUS Cyanea 
C. arctica, the sun-jelly or sea- 
blubber. This is the largest jellyfish 
known. Some individuals measure 
seven and a half feet across the disk 
and have tentacles more than one 
hundred feet long. Usually they are 
three to five feet in diameter, with 
tentacles thirty to forty feetlong. The 
disk is red, the margin white and scal- 
loped. The tentacles, of different 
colors, are covered with lasso- or sting- 
ing-cells, and are arranged in eight 
distinct, thick clusters on the margin. 
From the mouth hang four long and 
very broad, thin curtains, much folded 
and ruffled, whose edges at times look 
as if they were embroidered, because 
great numbers of discharged eggs are 
attached to them. Four egg-sacs hang 
from the disk near the manubrium, and 
eight sense-organs (tentaculocysts), in 
hardened coverings, lie in some of the 
deep incisions of the margin. Cyanea 
