BY DR. R. VON LENDENFELD. 235 



13. FAMILY HYDRA.CTINID.E. Von Lendenfeld, 1884. 

 Hydractinidae. Claus (1). 



Polypecolonies with free or rudimentary Medusae. The free 

 Medusae belong to Haeckels Sub-family Cytaeidae, and possess 

 Ocelli at the base of the tentacles, and no Otolithes. The tentacles 

 are scattered and equally distributed. With simple Moutharms. 



The Polype colonies consist of a dense mass of entwined Hydro- 

 rhizse from which the Hydrocauli, simple or slightly branched 

 grow forth. The alimentary Zooids possess one verticil of filiform 

 tentacles. The Medusae bud from the Hydrorhiza, or on mouth- 

 less Polyps, Polypostyles, rarely on the alimentary Polypes. Besides 

 the alimentary and Generative Zooids we meet with defensive 

 Spiral Zooids. (P. Wright.) 



I. SUB-FAMILY CYT^EUSLE. 

 Cytaeidse. Haeckel. 

 Producing free Medusae, which bud from the Hydrorhiza. 



SCHEMA : 



Ovum 



Medusa Polype Spiralzoid 



entwined Hydrorhiza, basal plate 



First Polype 



Ovum. 

 Cyteeis. Eschscholtz. 

 Cubogaster. Haeckel. 

 Dysrnorphosa. Philippi. 

 Cyteandra. Haeckel. 

 Corynopsis. Allman. 



II. SUB-FAMILY HYDRACTININ^. 



Medusae bud on Polypostyls, remain sessile and become rudi- 

 mentary (or immersed in the basal plate V) 



