102 



ELEMENTS OF BIOLOGY 



COELENTERATA 



N£MArOCYST 

 TENTACLE 



MOUTH 

 FEEDING HYDRANTH 



gonopoue 



reproductive 

 hydranth 



medusa bud 



MEDUSA 



(FREE SWIMMING 

 SEXUAL STAGE) 



COENOSARC 

 CASTROYASCULAR CAYITY 



FIG 33^. HYDROZOA-HYDROID OBEUA 



;'^y^^g 



'^>^^■^nMKx^^^>I^y 



GONADS 





ORAL ARM 



FIG. 34. SCYPHOZOA- AURELIA 



CASTROYASCULAR 

 CAYITY 



MESENTERY 



FIG. 35. ACTINOZOA- PORTION OF A 

 SEA ANEMONE 



Fig. 33b. — Hydroid Obclia, a colonial animal of the class Hydrozoa. Compare a 

 feeding hydranth with the structure of Hydra, Fig. 33b. (After Parker and Haswell: 

 Textbook, of Zoology, published by The Macmillan Co.) 



Fig. 34. — Class Scyphozoa illustrated by a common jellyfish, Aurelia. 



Fig. 35. — Illustration of the body structure of Actinozoa. The animal, Metndhim, 

 has been cut transversely to show the mesenteries which partition the gastro- 

 vascular cavity. The upper disk containing the mouth and tentacles is not shown. 



