Coelenterata. 327 



teries^* or intermesenteric spaces, as they are called. 

 There are holes through the mesenteries near the top, so 

 these chambers may communicate with one another. Be- 

 tween the mesenteries are ridges, extending inward from 

 the outer wall, but not reaching the gullet. These are 

 incomplete or secondary mesenteries. 



Change of Form of the Sea Anemone. When undis- 

 turbed the animal is cylindrical, sometimes long, some- 

 times broad, so that many of them resemble the flowers of 

 the chrysanthemum, daisy, anemone, and sunflower. They 

 well deserve the name, for many of them are beautifully 

 colored. The tentacles are often banded with variegated 

 colors. It is hard for one who has lived all his life inland 

 to realize that such brilliantly colored, flowerlike forms are 

 actually animals and not plants. But disturb one of these 

 flowerlike animals and it shows its real nature. It at 

 once begins to shorten, to withdraw its tentacles, and 

 shrink into a rounded mass lying close to its attachment. 

 The mesenteries are well supplied with longitudinal mus- 

 cles, whose shortening draws the body down close. Near 

 the margin of the disk are strong circular muscles which 

 shorten and shut in the free end, over the retracted ten- 

 tacles, like a bag with a draw-string, so that all that 

 appears resembles an old felt hat, with, perhaps, a little 

 indication of a hole at the apex. After the disturbance 

 ceases the sea anemone may gradually expand again. 



Development of the Sea Anemone. Sea anemones lay 

 eggs, which are developed in the mesenteries near their 

 free edges. The later development resembles that of the 

 jellyfishes, but there is no alternation of generations. 



General Characteristics of Sea Anemones. Sea anem- 

 ones are all marine. They are all single, that is, they 

 do not form colonies. They have no true skeleton. Some 



