26 CCELENTERATA AND 



peduncle which extends far outside the bell opening. Lips 

 quadrate. Ovaries ribbon-like on tubes and base of pe- 

 duncle. 



E. gracilis. 



B. II. 



Zygodactyla. Bell disk-shaped, cream colored, also 

 pinkish. Tubes numerous with ribbon-shaped ovaries. 

 Tentacles numerous, short, very flexible, generally coiled. 

 Sense-capsules numerous. Proboscis finger-like folds of a 

 delicate membrane which seldom closes forming the mouth 

 opening. Rows of small tubercles on the walls of the 

 bell-cavity between the chymiferous tubes. 



Z. Groenlandica. 



free-swimming larvae. 

 A.I. 



Pennaria gibbosa. The young Pennari-a closely re- 

 sembles the adult. This stage is rarely found free-swim- 

 ming on the surface, although if a colony of the hydroids 

 be kept in a glass jar for a short time, the buds if mature 

 easily drop off and swim away. 



Hybocodon prolifer. The larvae of this medusa can best 

 be studied by a comparison of the different medusa buds 

 found on the tentacular bulb of the adult. Free forms are 

 extremely rare and after they attain the stage when they 

 separate, their resemblances to the adult are very close. 



tStomatoca apicata. Larva like adult with tall bell which, 

 however, is destitute of apical prominence. Tubes four, 

 broad. Tentacles, two, opposite, long, very flexible. No 

 little tentacular projections on the bell-rim between the 

 tentacles. Proboscis shorter than in adult, extending to 

 the bell opening. 



Dinematella cavosa. Larva without apical projection 

 on bell apex. Cavity at base of the proboscis small, want- 



