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IX. 



Contributions to the Natural History of the Acaleph^ of North America. / 



By L. AG as SIZ. 

 PART I. — On the Nakcd-cycd Medusa of the Shores of Massachusetts, in their T erf eel State of Development. 



(Communicated to the Academy, May 8th and May 29</j, 1849.) 



There is a deep scientific interest connected with the study of Medusce. Notwith- 

 standing their slight consistency and their extraordinary transparency, a highly organized 

 structure has been observed in many of them ; and, though the most opposite opin- 

 ions still prevail among observers respecting the signification of the facts thus ascer- 

 tained, it is not the less evident that their structure deserves to fix the attention of 

 physiologists in the highest degree. It is, in reality, one of the most wonderful sights 

 which the philosophic naturalist can behold, to see animals scarcely more dense than the 

 water in which they play, and almost as limpid, perform in that medium movements as 

 varied as those of the eagle which soars in the air, or of the butterfly dancing from 

 flower to flower, testifying by their activity their sensitiveness and their volition. 

 Their mode of living, as far as it is known ; their periodical appearance, like annual or 

 biennial plants ; their rapid growth ; the short duration of their life ; the brightness or 

 softness of the light which they emit during night, and which illuminates even the deep 

 ocean ; the wonderful facts which have been ascertained respecting their mode of repro- 

 duction ; — all this is of a character to strike, in the highest degree, the curiosity even of 

 the most careless. It is, therefore, not surprising, that, from time immemorial, the phos- 

 phorescence of the sea, which is, in a great measure, owing to the presence of jelly- 

 fishes, should have excited the deepest interest, and that, of late, the natural history 

 of Medusae should have become one of the most fascinating subjects for the ablest scien- 

 tific observers, and opportunities to trace and repeat their researches, a matter of the 

 most ardent desire on the part of inland naturalists, whose curiosity has been excited 

 to the utmost by the narrative of so many wonders. 



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