STROBILIZATION OF AURELIA 97 



normally to give rise to ephyrae. The two rudiments below 

 these, however, produced eight tentacles each and no lobes. 

 The oral disc did not undergo any change except that it became 

 separated from the rest and lay on the bottom of the dish. 

 There was a large apical opening the presence of which suggested 

 that the disc had been prematurely separated. After some 

 days the hole closed and the tentacles were absorbed. No 

 lobes developed and later a pedal stalk grew out from the 

 apical end, the body ultimately becoming attached to the floor 

 of the dish. Later four perradial tentacles appeared and the 

 whole had the form of a normal scyphistoma. The next two 

 rudiments proceeded normally and produced ephyrae which 

 were subsequently liberated. 



The rudiments possessing tentacles then became free and 

 moved over the surface of the dish for about a week by means 

 of the flagellated surface, one of them revolving, the other 

 progressing in a more or less straight line. Later each grew 

 a foot stalk from the apex and became attached to the vessel. 

 In the meantime one had increased the number of tentacles to 

 twelve. 



A second young strobila also behaved in an unusual manner. 

 Here the two segments next to the oral disc gave rise each to 

 four tentacles and no lobes. They, along with the oral disc, be- 

 came separated in a body and remained attached to each other 

 while on the floor of the dish. The oral disc did not appear 

 to undergo any change, but the other two segments gradually 

 absorbed their tentacles and became converted into a long 

 narrow stalk at the end of which w^as a pedal disc. Attach- 

 ment with the dish was effected, the stalk became stouter, and 

 the whole body assumed the form of a normal scyphistoma. 



The occurrence of segments which give rise to polyps leads 

 one to believe that there is a distinct difference between these 

 and the ephyra rudiments. It may be that they have been 

 derived from ephyra rudiments, the sequence of changes 

 necessary to produce an ephyra having been interrupted or 

 reversed, or they^may be different from the start. Again, it 

 may be that up to a certain point the segment may be regarded 



NO. 265 H 



