MEDUSA BIFIDA. 129 



I. The Hydra tuba is a real marine polypus, as distinguished by the 

 identical properties characterizing the two species, viridis siaiftisca, dwell- 

 ing in the fresh waters of Scotland. 



II. It feeds after the same manner : its offspring are generated after 

 the same manner, by a bud from the side of the parent, which offspring 

 matures, establishes itself independently, and demonstrates precisely the 

 same nature. 



III. Both these marine and fresh-water hydrae are apparently perfect 

 animals : they undergo no metamorphosis from the moment the bud is 

 evolved into form ; and they survive during years. 



IV. Their nature corresponds in the tenacity of life : they enjoy to 

 the utmost extent the property of recovering mutilated parts. 



V. At an indefinite period, and under indefinite circumstances, a 

 pendulous roll or column is observed, as if implanted on the disc of some 

 of a colony of the Hydra tuba. 



VI. The pendulous column is a roll of embryo Medusae, resting in its 

 earlier stage upon, or attached to, a smooth fleshy bulb. 



VII. It is faintly indented by circles, and is terminated by a circular 

 row of tentacula. 



VIII. The indenting circles become deeply waved, the tentacular or- 

 gans at the summit of the roll are obliterated. 



IX. The circumferential waving indicates the evolution of Medusae, 

 which are farthest advanced towards the summit. From their enlargement 

 the roll becomes a conic frustum, sustained by the fleshy bulb. 



X. The Medusae successively attain maturity : they struggle vehe- 

 mently towards the extremity of the roll for liberation. A new circle of 

 tentacular organs, prominent before disappearance of the old circle, and 

 distant from it, is now evolving from the bulb. 



XI. The Medusa? are successively liberated, and by their maturity 

 and liberation the embryonic roll is dissolved. 



XII. The season of their generation, production, and liberation, is 

 limited by about 60 days, wherein the month of March is comprehended. 



XIII. The period of their survivance, when free, does not exceed 

 60 days in confinement. 



VOL. I. B 



