346 THE AUSTRALIAN HYDROMEDI'S.T-: . 



THE EEEE SWIMMING MEDUSA HAVE A CENTEAL- 

 IZED DOUBLE NEEYE-EING, A VELUM, NO MAEGINAL 

 FLAPS AND NO ENTODEEMAL FILAMENTS IN THE 

 GASTEAL CAVITY. THESE MEDUS7E BUD ORIGINALLY 

 ON POLYP COLONIES, BUT MANY OF THEM HAVE 

 TAKEN TO A DIRECT DEVELOPMENT "WITHOUT 

 INTEEMEDIATE POLYP COLONIES. 



FEEE SWIMMING POLYP COLONIES ALWAYS 

 POSSESS A CHITINOUS SKELETON (GEAPTOLITH- 

 ID2E.) 



I.— SUBORDO HYDKOPOLYPIN^E. Von 



Lendenfeld, 1884. 



HYDROMEDUS.E, WHICH MULTIPLY BY BUDDING AND BY 

 SEXUAL PRODUCTS, WHICH DO NOT APPEAR IN THE SHAPE 

 OF MEDUSAE. THE BUDDING POLYPES MAY BE DISINTE- 

 GRATED FROM THE PARENT AND SO ALL REMAIN SOLITARY, 

 OR THEY MAY REMAIN ATTACHED AND SO FORM A COLONY. 

 IN BOTH CASES SEXUAL MULTIPLICATION ALTERNATES WITH 

 THE PROCESS OF BUDDIKG. 



THE SEXUAL PRODUCTS ARE MATURED IN THE WALL OF 

 THE BODY-CAVITY, WHICH MAY FORM HOLLOW TENTACULAR 

 PROCESSES IN WHICH THE OVA AND SPERMATOZA ARE 

 FOUND. ORIGINALLY ALL POLYPES ARE SEXUAL. IN SOME 

 HYDROPOLYPIN^E ONLY SOME OF THE MEMBERS OF A COLONY 

 MATURE THE SEXUAL PRODUCTS, AND THESE BECOME 

 ADAPTED TO THE PURPOSE AND DIFFERENT FROM THE NOW 

 EX( LUSIVELY ALIMENTARY ZOOIDS. IN THIS PROCESS THEY 

 LOOSE MOUTH AND TENTACLES AND SO BECOME POLYPO- 

 STYLES, WHICH ARE IN SOME CASES SO SIMILAR TO RUDI- 

 MENTARY MEDUS.E, THAT SUCH SPECIES MIGHT ALSO BE 

 PLACED, AND PERHAPS WITH GREATER ADVANTAGE, IN THE 

 SECOND SUBORDO HYDROMEDUSINJE. IN SOME CASES, SOME 

 POLYPES ARE ALSO TRANSFORMED INTO DEFENSIVE MACHO- 

 POLYPS WITHOUT A MOUTH. 



This Suborder comprises forms which have hitherto been 

 separated widely from each other, but as I think, only because an 

 undue weight was attached to the structure of the chitinous 

 exoskeleton, which invests sometimes only the stem and branches 



