SEA-BLUBBERS. 



85 



The little creature is now a polype of four tentacles. 

 We have not been able to trace the development further 

 in this species, but the deficiency has been supplied by the 

 observations of others upon the larger genera. 



The most common — or, at least, the best known — Me- 

 dusa in the British seas is the Aurelia aurita, that Sea- 

 blubber, with four imperfect rings of pink in the disk, 

 which is so often seen floating in our harbours, or washed 

 ashore on our beaches. In this species the whole progress 

 of development, from the first appearance of the ova to 

 the formation of perfect Medusse, has been traced by 

 several observers, and the following is an epitome of the 

 highly curious facts. 



The pink semi-rings are the ovaries, in which the ova 

 are first developed. At a certain early stage they are 

 transferred to four pouches beneath the arms, where they 

 increase in size, become granular in texture, and at length 

 assume the figure and manners of an oblong Infusorium. 

 As each one quits the maternal pouch, it swims freely away 

 by the aid of its investing cilia, with its larger end fore- 

 most. Soon, however, it selects a place of rest, to which 

 it adheres by its smaller extremity, and quits the roving 

 for the stationary life. 



A depression now forms in the thicker end, which 

 deepens and becomes a digestive cavity ; while the margin 

 expands and buds out into four processes, which are 

 strongly ciliated. Up to this time it had been yellowish 

 and opaque ; it now becomes colourless and transparent. 

 Four other processes are now formed in the interspaces 

 of the former four ; so that the little animal now closely 

 resembles a Hydra with eight tentacles, especially as these 



