JELLYFISHES AND HYDROIDS 33 
find feeding polypites, reproductive polypites and tentacles very 
much as in Velella. 
Porpita is rare along our coast, but between Cuba and South 
Carolina it is sometimes so abundant as to fleck the ocean for miles 
with specks of brilliant blue. 
The Sea-Blubber, ( Cya- 
nea arctica), is the largest 
known jellyfish. In the cold 
waters north of Cape Cod it 
grows to huge proportions, 
and one was found by Dr. 
Alexander Agassiz which 
measured seven and one-half 
feet across the disk and 
whose tentacles were fully 
one hundred and twenty feet 
long. On the Long Island 

coast, however, it grows to Fig. 9; MILKY-DISK JELLYFISH, 
a much smaller size and Ngneyard Soon 
thrives only in spring and early summer, disappearing about the 
middle of June Large as these creatures are, however, when 
dried in the sun it is found that the animal substance is only 
z27 part of the whole; the vast bulk of the creature’s body being 
composed of sea water. 
The disk is amber-colored with a rosin-colored centre marking 
the stomach-space. There are sixteen notches at regular intervals 
around the edgeof the disk, and eight of these notches are occupied 
by sense organs which contain granular concretions. 
On the lower surface of the disk one finds the central mouth 
surrounded by veil-like lips, and eight clusters of tentacles. 
The eggs are caught in the veil-like folds of the lips and set 
free as little pear-shaped larvee which swim rapidly through the 
water by means of their cilia. Soon, however, each larva settles down 
upon the bottom and develops into a polyp having a terminal mouth 
surrounded by tentacles. After feeding and growing for some 
months the polyp begins to display constrictions at regular inter- 
vals, and soon it splits up into a series of disks, each one of which is 
set free and becomes a jellyfish. 
