ALTERNATION OF GENERATIONS. 303 



larges into a little sac, I perceived two minute granules, 

 which quivered and jerked about in a vacillating but 

 rapid motion, just as if under the influence of a strong 

 current, they not being free to be carried along by it. 



The substance of the globe carries many scattered 

 oval bodies, apparently imbedded in it. They are 

 very minute, are set with their long diameter always 

 pointing from the centre, but are not arranged re- 

 gularly. 



I need scarcely say that this embryo of the Sertu- 

 larian Zoophyte, Cainpanularia, like that of Laomedea 

 before described, is a veritable Medusa ; in no essen- 

 tial point to be distinguished from those Naked-eyed 

 forms so exquisitely figured and described by Pro- 

 fessor Edward Forbes, in his beautiful Monograph. 

 And the case is illustrative of one of the most startling 

 and most interesting series of facts that modern science 

 has discovered, those connected with the Alternation 

 of Generations. Here is a fixed and celled Polype, 

 giving birth to free-swimming Medusse ; hereafter 

 we shall have occasion to describe a Medusa produc- 

 ing an embryo which presently assumes the form of a 

 fixed and celled Polype. In both cases, the law ap- 

 pears to be established, that there is an alternate put- 

 ting on of the two forms by successive generations ; 

 neither the one nor the other being a phase in meta- 

 morphosis, like the caterpillar, and chrysalis of a 

 butterfly, but each form producing the other in the 

 way of generation; and thus, as has been cleverly 

 said, any one individual is not like its mother or its 

 daughter, but is exactly like its grandmother and its 

 grandaughter. 



