MORPHOLOGY OF INVERTEBRATE TYPES 



of Aurelia one cannot fail to notice four interradial, oval openings 

 which appear as if they were leading into the gastric pouches. 

 In reality they lead into blind subgenital pits situated under the 



gastric pouches. The 

 pits are lined with ec- 

 toderm and have no 

 connection whatever 

 with the gastric 

 pouches. Neither have 

 they anything to do 

 with the reproductive 

 functions of Aurelia. 

 It is probable that the 

 subgenital pits help 

 respiration inasmuch 

 as they increase the 

 surface of the subum- 

 brella and allow the 

 water to come nearer 

 to the reproductive 

 organs. 



FIG. 8. Tentaculocyst of Aurelia aurita, 

 longitudinal section. Diagram after Eimer, 

 from E. Ray Lanckester's Treatise on Zo- 

 ology. A, aboral (superior) olfactory pit; B, 

 adoral (inferior) olfactory pit; c, exumbrella; 

 Con, statocyst; Ent, radial canal continued 



into tentaculocyst; End, endoderm; Oc, ocellus; 

 T, tentaculocyst; Or, subumbrella; H, bridge 

 between the two marginal lappets (hood). 



Nervous system. 

 The nervous system 

 consists of a subepi- 

 thelial network of gangl ionic cells and fibres and of eight 

 nervous centres or ganglia, one at the base of every rhopalium. 

 The subepithelial network is found in the subumbrella between 

 the epithelial layer and the layer of muscular fibres. The func- 

 tion of this network is chiefly that of a motor system. 



Sense organs. We have seen that Aurelia has eight 

 marginal sense organs or rhopalia. A rhopalium is a very com- 

 plicated organ with various functions. It is protected by the 

 two marginal lappets and its cavity stands in direct communica- 

 tion with the circular canal. The rhopalium itself consists of a 

 large dorsal protective fold or hood with the aboral olfactory pit 



