Fig. 77- — DiaL^r.ims illustrating the derivation t..r the medusa from the hydrantli. 

 In the whole series of figures the ectoderm {eci) is dotted, the endoderm {Cfui) 

 striated, and the mesoglcca O'ls^i) black. 



A, longitudinal section of a simple polyp, showing the tubular body with enteric 

 cavity (fft/. ca7'), hypostome i/tv/>), mouth {711th.), and tentacle.s (/). 



\\ trans\'erse section of the same through the plane ab. 



B, the tentacular region is extended into a hollow disc. 



C, ihr- irntflcular region has been'fiuther cxtcm.kd ,uid benl 11, m .t bfll-likc fi'iin 



