92 



THE HYDROIDS AND HYDROMEDUSiE 



free-swimming medusa, reproducing by syngamy. How could the 

 life-cycle of an extensively budding hydra be modified to give stages 



® i 



ovum £>perm 



Fig. 45. — The life-cycle of Obelia, showing alternation of generations. A, por- 

 tion of a colony of Obelia. B, develoi)mcnt of a colony following attachment 

 of the planula. a, zygote; b, two-cell stage; c, four-cell stage; d, blastula. 



comparable with those in the life-cycle of the obelia? Construct a 

 table or a full-page diagram comparing the life-cycles of the obelia 

 and hydra. 



