JELLYFISHES AND HYDROIUS 



33 



Fig- 9, 



MILKY-DISK JELLrFISII, 

 Vinej'ard Sound. 



find feeding polypites, reproductive polypites and tentacles very 

 much as in Velella. 



Forpita 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. 



TheSea-Blubber/Cf/n- 

 nea nrctieaj, is the largest 

 known jellylish. In the cold 

 waters north of Cape Cod it 

 grows to huge proportions, 

 and one was found l)y 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 

 a much smaller size and 

 thrives only in spring and early summer, disappearing about the 

 middle of June, Large as tliese creatnres are, however, when 

 dried in the sun it is found tliat the animal substance is only 

 y-j-^ part of the whole; the vast bulk of tlie 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 wlilcli contain graniilar 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-liivc folds of tiie lips and set 

 free as little pear-shaped larva; Avhich 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. 



