100 



INVERTEBRATB MOBPEOLOOT. 



being lined by sensory cells to which an olfactory function is 

 attributed. The marginal sense-organs of the Scyphomedusse 

 are thus much more complicated in structure and in addition 

 have a different mode of origin than those of the Hydrome- 

 dusse. 



1. Order Stauromedusse. 



In this order some of the forms are fixed throughout their 

 adult life, e.g. Zmernaria (Fig. 52) ; while others are free- 

 swimming when mature, as Tessera. The deep bell has at 

 the margin eight tentacles — the primary tentacles, none of 

 which become modified into sense-organs, these structures 

 being wanting in the group. In some species of Lvcernaria 



Pig. 53. — naliclystus auricula divided longitudinally (after H. James-Clark). 

 / = funnel. mf = mesenterial filaments. 



go = reproductive organs. 

 ia = iuterradial adhesion. 



rp = radial pouch. 

 i = modified primary tentacle. 



these primary tentacles {t) are somewhat altered, and in all 

 the margin of the bell is produced into eight knob-tipped 

 lobes, to each of which a bunch of secondary tentacles 

 may be attached. The coelenteron extends out to the margin 

 of the bell, and is interrupted along the interradii by a point 



