IV 



COELENTERATA 



75 



the summer. This is very much the same pheuomenon as the 

 " strobilization " of the Soyphistoma, when the first " Ephyra-head " 

 is budded off. 



Fig. 55.— Longitudinal section tliroiigli the sense organ of a young Ephyra. 



calc, calcareous concretions in tlie sense-tentacle ; I, lobe of disc of Ejiliyra ; r.c, wall of radial canal ; 



(C7(i, sense-tentacle. 



Fig. 56. — Three stages in the development of the Ephyra larva into the adult Aurelia. 



(After Glaus.) 



ad, adradial cushion ; c,e, circular canal ; g.f, gastral filament ; I, lobe sheltering sense tentacle ; 

 per, per-radial canal ; teii^, sense-tentacle. (The reference line without letter in the first figure points 

 to an inter-radial canal.) 



Then in both groups the sexually mature person is typically a 

 person which breaks loose from the colony and develops a swimming- 

 web. In Hydrozoa such a person breaks loose in such a way as 



