DEDUCTIONS. 89 



2nd, an alteration in the figure of its body from the 

 formation of a roll of embryonic Medusae on the disc ; 

 3rd, the gradual maturation of each Medusa, and its 

 liberation from the roll ; 4th, the disappearance of 

 the original tentacula of the Hydra ; 5th, the emer- 

 ging of a new circle of tentacula from a smooth fleshy 

 bulb sustaining the embryonic roll ; and lastly, the 

 evolution of this fleshy bulb as a perfect Hydra, which 

 becomes the parent of other Hydrse by gemmation, 

 and remains permanent as an independent animal. 



All the Medusse in the embryonic roll are separate 

 and distinct beings; each is in close application to 

 that which is next below if itself be uppermost, or 

 lies between two if intermediate. The proboscis is 

 outermost if the individual be uppermost in the pile ; 

 thus all lie in the same direction, the proboscis outer- 

 most, as the Medusa escapes from the next left be- 

 hind. When the last remains adherent to the fleshy 

 bulb, its proboscis projects outwards also. Thus the 

 under-surface of the embryo is always outwards while 

 it forms a portion of the roll, an arrangement which 

 evidently shows that the maturation of the embryos 

 and their liberation into active life must be successive. 



