HYDROID.E : TUBULARIDjE. 



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 

 restricted by Agassiz, embraces on- 

 ly hydroids whose head is furnished 

 with a wreath of simple coronal ten- ct 

 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 Tubularia, Thamnocni- 

 dia, and Parypha have the medusae 

 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- Tubularia Couthouy ^ Ag 

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



tn, medusae ; ct, coronal ten- 

 tacles ; />, proboscis. 



504- 



Campanularian, Obelia commissuralis, 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 



