IV 



COELENTERATA 



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

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



is budded off. 



ten 



FK;. 55. Longitudinal section through the sense organ of a young Ephyra. 



mh-, calcareous concretions in the sense-tentacle ; 1, lobe of disc of Ephyra ; r.c, wall of radial canal ; 



/<'//!, sense-tentacle. 



Fin. 56'. Three stages in the development of the Ephyra larva into the adult .1 urelia. 



(After Claus.) 



ad, adradial cushion; c.c, circular canal; g.f, gastral filament; I, lobe sheltering sens.' trutudi' ; 

 per, per-radial canal ; ten 1 , sense-tentacle. (The reference line without letter in I he' lirst li^uie 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 



