MEMOIRS 



OF THE 



BOSTON SOCIETY OF NATURAL HISTORY: 



VOLUME III, NUMBER XII. 



THE LIFE-HISTORY OF THE HYDR0MEDUSJ1 : 

 A DISCUSSION OF THE ORIGIN OF THE MEDUSAE AND THE SIGNIFICANCE 



OF METAGENESIS. 



WITH PLATES XXXVII-XLIV. 



Br W. K. BROOKS, 

 Johns Hopkins University, Baltimore, Md. 



BOSTON": 



published by the society. 

 June, 1886. 



