206 



PRACTICAL ZOOLOGY 



122 will make the following description clear. The hydralike 

 members of the hydroid colony arise asexually by budding and 

 serve to capture and digest food. Occasionally buds of a dif- 



Fig. 122. — A, part of a colonial ccelcnterate. 1, ectoderm; 2, entoderm; 

 3, mouth; 4, ccelenteron; 5. ccenosarc; 6, perisarc ; 7, hydrotheca ; 8, blasto- 

 style ; 9, medusa-bud ; 10, gonotheca. 



B, free-swimming medusa: 1, mouth; 2, tentacles; 3, reproductive 

 organs ; 4, radial canals ; 5, statocyst. 



C, larva (planula). (From Parker and Haswell.) 



ferent sort are formed; these undergo a second budding, but 

 the buds thus produced do not remain attached to the colony. 

 When they reach their full size, they separate from the parent 



