JELLYFISHES AND HYDROIDS 39 



bles a delicate seaweed or plume, but is in reality an animal. Each 

 branch gives rise to a number of little flower-like polyi>moutlis 

 surrounded by tentacles which cajjture prey. 



Jellyfishes develop within capsules at the angles of the stems. 

 These jellyfishes are set free and swim about for a long time, 

 finally growing to be about one-quarter of an inch in diameter. 

 Then they cast out their eggs which develop into jDlume-like liy- 

 droids which in turn give rise to jellyfishes. 



The Rainbow Jelly, (Mncmiopsis leidijij, is one of the comb- 

 jellies or CtenopTiorcc. It is exceedingly abundant along our coast 

 during the summer, but is so transparent that it would escape 

 observation were it not for the brilliant flashes of prismatic red 

 and green that play over its eight rows of comb-like flappers. 

 When full grown the creature is about four inches long, and 

 the outline of the body is pear-shaped with broad wings on the 

 sides. At the narrow end there is a sense organ consisting of a 

 capsule filled with a ball-like mass of concretions. This sense 

 organ enables the creature to maintain its proper position in the 

 water. The central stomach gives rise to a complex system of 

 ramifying tubes which extend through the wings and along under 

 the eight rows of combs. This creature is so delicately formed that 

 it can not be lifted from the water without serious injury, yet it 

 readil}^ captures small fish and Crustacea upon which it feeds. At 

 night it gives out a brilliant green phosphorescence when disturbed. 



One often finds a long, pink, worm-like parasite imbedded 

 within the gelatinous substance of the Rainbow Jelly. This is not 

 a worm, however, but is a sea anemone, Edwardaia leidyi. 



