COELENTERATA 



33 



The medusa l is transparent and of a jelly-like consistence, 

 owing to the great thickness of the gelatinous layer, known 

 as the mesogloea, which lies between the skin and digestive 

 cells. (Compare Hydra, p. 25.) 



In the wall of the bell there is at first a continuous 



FIG. 14. Bougainvillea. 



A, Colony natural size; B, colony enlarged ; C, single reproductive individual or 

 medusa ; p, nutritive polyp ; g, a medusa bud. 



cavity, lined with digestive cells ; but, after a while by the 

 closing together of the inner and outer parts of the wall 

 except just at the top and along four radial lines and also 

 along the margin of the bell the cavity is restricted to a 

 central chamber, communicating with the exterior by the 



1 These medusae can readily be obtained, late in the summer, by drawing a 

 muslin net behind a boat, or even by skimming the surface of a rock pool with 

 a net, and then dipping the net into a pail of sea-water. They are so small 

 and so transparent that they may be overlooked at first. They vary in size 

 from a mere speck, to a ball \ an inch in diameter. 



VOL. I D 



