56 NATURAL HISTORY OF OUR SHORES 



termed the manubrium. At the lower end of this is the 

 mouth, and from its sides project, sometimes simple, some- 

 times complicated and lacelike, what are termed the Gastric 

 filaments. 



The reproductive organs are on the under side of the 

 umbrella, and within the membrane ; below these are four 

 hollows or pockets " subgenital pits." 



This brief review of their general plan will suffice for 

 our purpose. 



Amelia aurita is a very common species. It is rather 

 flat-shaped, and about four to six inches in diameter. 



It can be recognised at once, as it floats on the sea, by its 

 having four circular rings (these mark the reproductive 

 glands) of a purple colour, each about the size of a penny 

 piece, and so arranged that their edges touch one another. 



The reproduction of Aurelia has been well studied, and 

 it gives a key to the reproduction of the others, although 

 the methods are not quite identical. 



An egg from the parent develops into a little ciliated 

 embryo, which for a time floats freely in the sea, then 

 settles down upon a rock or a stone and becomes fixed. 

 It grows upward, broadening towards the top. Then 

 sixteen tiny tentacles appear around the edge, so that it 

 looks like a little anemone about one-sixteenth of an inch 

 across. It still grows taller, in shape like a little inverted 

 sugar-loaf. Then a series of constrictions appears on the 

 column (this process is termed Strobilation) , dividing it 

 into a number of discs, the top ones each having a row 

 of tentacles. The organism is now like a pile of saucers 

 of graduated sizes, the largest at the top. Then the top 

 one breaks away, and is followed at close intervals by the 

 succeeding ones, as each attains the proper size. These 

 little freed discs are termed Ephyrce, and they rapidly grow, 

 and assume the characters and functions of the adult 

 Aurelia, developing eggs, and repeating the life cycle. 



