58 COELENTERATA 



The scyphistoma grows, acquires more tentacles, may bud 

 to form other scyphistomae, and usually acquires stolons, 

 which grow out from the body wall just above the base. 

 From the stolons new scyphistomae arise. Subgenital pits 

 make their appearance in the position formally occupied by 

 the septal funnels, and an ostium appears in each taeniole 

 near the oral surface. In this way a ring sinus is formed. 

 Gastric filaments are formed on the edges of the taenioles. 



From the oral side of the first eight tentacles, sense organs 

 bud out. Eight lobes make their appearance opposite these 

 sense organs, each lobe divides into two lappets, between 

 which the sense organ lies. While these changes are taking 

 place constrictions running around the body appear and 

 deepen so the body is divided into a series of plates, each 

 of which has eight lobes, eight sense organs, and sixteen 

 marginal lappets. The disk at the free extremity is the oldest 

 and most differentiated. 



This stage is frequently called the strobila, but there is no 

 definite dividing line between scyphistoma and strobila. The 

 number of disks formed by a strobila seems to be dependent 

 upon conditions, probably largely food supply. 



Before the disks are ready to be detached as ephyrae the 

 tentacles disappear. Ephyrae are detached one at a time 

 from the free end as they mature. 



Up to this point students will be able to determine only 

 part of the points mentioned unless an abundance of material 

 and sections are provided. The remaining points are easily 

 determined. 



Examine a free ephyra. If it is alive, watch it swim. Find 

 the mouth, stomach, marginal lobes, marginal lappets, and 

 sense organs. Use these as landmarks to determine the rela- 

 tion of parts to the adult. Are there any outgrowths from the 

 stomach? Do the sense organs have any relation to branches 

 from the stomach? Can you find gastric filaments? 



From the shape of the mouth determine which of the lobes 

 are perradial and which interradial. What part of the adult 

 is represented by the notches between the lobes? 



