The Development of Scyphomedusse. 245 



Later Development 

 The Planula 



No attempt will be made to give technical details on phases 

 of later development. There are yet problems involved in some 

 of these which merit careful attention, and we much regret that 

 our material does not include that necessary to such a study. 

 It seems, however, that some brief review of a few points may 

 be of value. 



Referring to this phase Professor Agassiz has expressed views 

 which seem more or less open to question. For example, concern- 

 ing the time and circumstances associated with spawning he says, 

 ''it might be supposed that the great destruction of these animals 

 by the autumnal gales would put an end to the development of 

 the eggs of the stranded specimens, but this is not necessarily the 

 case. On the contrary, I believe .... that the coincidence of 

 their spawning with the stormy season of the year is a provision to 

 bring them into proper conditions for their future development 

 and growth. Thrown among the rocks, upon the seaweeds, they 

 become entangled and break up; but: by the time they are in 

 pieces the eggs, which have been accumulating in the little pouches 

 formed by the folds of the margin of the arm, have reached their 

 planula state, and are ready to swim about independent as animals 



as soon as they are cast off As with the returning tide 



such specimens are set afloat again, it is evident that their brood 

 may frequently make its escape into the water and undergo their 



normal development after having been for a time ashore 



The young soon become attached to rocks, dead shells, or sea- 

 weeds, and assume their polyp-like condition. . . . . The 

 succession of fine days, along our shores during the month of 

 October following the equinoxial gales, is the season during which 

 the planulse, set free by the decomposition of their parents, 

 float about in search of a resting place." It is hardly necessary 

 to point out the teleologic bias which vitiates this account. And 

 it is only necessary to point out that while it might be plausible 

 if only Aurelia were concerned, what shall be said of Cyanea or 

 others whose spawning season is April instead of August? 



