AURELIA. 43 



pouches. The males and females in this kind of Jelly-fish may 

 be distinguished by the difference of color in the reproductive 

 organs, which are rose-colored in the males, and of a dull yellow 

 in the females. The process of development is exactly the same 

 in the Aurelia as in the Cyanea, though there is a very slight 

 difference, in their respective Hydroids. They are, however, so 

 much alike, that one is here made to serve for both, the above 

 figures being taken from the Hydroid of the Aurelia. It is 

 curious, that while, as in the case of the Aurelia and Cyanea, 

 very dissimilar Jelly-fishes may arise from almost identical Hy- 



droids, we have the reverse of the proposition, in the fact that 

 Hydroids of an entirely distinct character may produce similar 

 Jelly-fishes. 



The embryos or little planulae, hatched from the Cyanea and 

 Aurelia in the fall, seem to be gregarious in their mode of life, 

 swimming about together in great numbers till they find a suit- 

 able point of attachment, and assume their fixed Hydroid exist- 

 ence. The Cyanese, however, when adult, are usually found 

 singly, while the Aurelige, on the contrary, seek each other, and 

 commonly herd together. 



Fig. 50. Aurelia flavidula, seen from above ; o mouth, e e e e eyes, mm mm lobes of the mouth, 

 oooo ovaries, tttt tentacles, w w ramified tubes. (Agassiz.) 



