VIII. The Ephyrula . 

 The medusa that is set free from a strobila of Cassiopea 

 has a very different appearance from the ephyrula stage in jel- 

 ly-fish that have eight, the usual number of rhopalia. Coty- 

 lorhiza has an ephyrula resembling the same stage in the sem- 

 ostomatous medusae. Good figures of this are given by du Pies- 

 sis and Glaus and there is a striking difference between these 

 figures and my Figs. 21 and 22 which are camera drawings of 

 well preserved ephyrulas of Cassiopea mounted in balsam. Fig. 

 21 represents a young Cassiopea that has not long enjoyed a 

 free existence. The general shape of the i;mbrella is like 

 that of the adult, and there is the same concavity in the cen- 

 tre of the exumbrella, while the margin curves in the opposite 

 direction, as in Fig. 52. The typical ephyrula of Aurelia or 

 Gotylorhiza has eight marginal arms with two lobes at the end 

 of each and between these, a rhopalium. In Casiopea struc- 

 tures corresponding to these arms are present to the number of 

 sixteen, or often more. But these do not destroy the gener- 

 al circular outline of the animal for they are connected by 

 thin areas in the jelly with an equal number of ridges alter- 

 nating with them, which at an earlier stage bore the interrho- 



51 - 



