THE SCYPHOMEDUSAE 



69 



ments thus indicated, eight bifid lobes grow outwards, each lobe 

 carrying with it the attachment of either a perradial or interradial 

 tentacle. The bases of these tentacles are stated to be converted 

 into the tentaculocysts of the adult medusoid, the eight adradial 



Aurclia aurita, from the oral surface. 1, mouth; 2, perradial oral arms; 3, marginal 

 tentacles ; 4, perradial branching canal ; 5, adradial straight canal ; 8, circular canal ; 9, ten- 

 taculocyst; 11, interradial gastric lilanients and generative organs. The subgenital pits are 

 not shown in the drawing ; the oral arms have been slightly twisted out of their perradial 

 position. (From Shipley, after Claus.) 



tentacles disappearing altogether. A prolongation of the coelen- 

 teron, which will form the axis of the future perradial and inter- 

 radial canals of the adult, runs out into each lobe. At about this 

 stage the entire segment becomes constricted off from the Scyphi- 

 stoma, and leads a free -swimming existence as an Ephyra, the 

 larval form of the future medusoid. Of the lower segments of 

 the Scyphistoma, some, if not all, may also put out sixteen ten- 

 tacles, and all become constricted off as Ephyrae. The basal 

 unconstricted part of the Scyphistoma is stated to become again 

 tentaculate, and to remain quiescent till the next season, when the 

 process of strobilation is repeated. 



In the Ephyra (Fig. 6, E, E) the adradial spaces between the 

 lobes gradually fill up by centrifugal growth of the disc, and eight 



