HYDROIDS : TUBULARID^E. 



515 



and branch until a community of hydroids resembling a 

 tuft of moss has grown up, Fig. 499. From these hy- 

 droids, in turn, bud the free medusae, like Fig. 501. 



TUBULARID.E. This Family, as Fig. 502. 



restricted by Agassiz, embraces on- 

 ly hydroids whose head is furnished 

 with a wreath of simple coronal ten- 

 tacles, and a proboscis with simple 

 tentacles around the mouth ; and 

 which produce either persistent or 

 free medusae, more or less one-sided, 

 budding from the floor between the 

 coronal tentacles and the proboscis. 

 The Genera Tnbnlaria, TJiamnocni- 

 dia, and ParypJia have the medusas 

 persistent ; Hybocodon free. 



The Sub-Order of Sertulariae em- 

 braces those in which the hydra is 

 always pedunculated and attached, 

 and protected by a horny sheath 

 forming a cup around the head ; and 

 the medusae are either free or persist- 



Tubulana Couthonyi, Ag. 



ent, generally flat, but in some cases Massachusetts Bay. 



m. medusae ; cf, coronal ten- 

 Fie 505 



tacles ; /, proboscis. 



Fig. 54- 



Campanularian, Ohelia commtssurahs, McCr. 

 The hydro-medusae in the cups drop out and be- 

 come free medusae, similar to Fig. 504. Atlantic 

 coast of North America. 



Campanularian, 



Tiaropsis diademata^ Ag. 



Northeast coast of North America. 



bell-shaped, and furnished with numerous tentacles. This 



