a thickened area of the ectoderm at the apex ol' the bud. Fig. 

 28. At this point the suiporting jelly is very thin, so that 

 the entodei-m ana ectouerm are almost in contact. The bud grad- 

 ually increases in size, becoming hemispherical and then elon- 

 gating. As it elongates, a constriction appears close to the 

 body of the scyphistoma, and now, while the bud continues to 

 elongate, it alters its shape and the constriction deepens, 

 cutting off the lumen of the bud from the digestive cavity of 

 the scyphistoma. The result is an obversely pear-shaped body 

 attached to the scyphistoma by a very narrow isthmus of sup- 

 porting substance covered by ectoderm. Fig. 19. Sometimes a 

 second bud will appear before the first one has dropped off. 

 In this case the second bud has always the same point of ori- 

 gin as the first, so that in such specimens the first bud is 

 attached to the apex of the second one. Fig. 1. I 



1 1 . The_ Planula - like Larva . 



The bud is finally constricted off while it is still a 

 simple, pear-shaped, or perhaps more properly, acutely egg-sha- 

 ped body, without trace of mouth or tentacles and immediately 

 becomes a pleinula-like, free swimming larva. Like a planula, 

 its whole surface is covered with cilia, and in swimming it 

 rotates from right to left upon its long axis, which is paral- 

 lel to its line of progression. 



- ?,5 - 



