STEENSTRUP'S THEORY. 317 



C. These Polypes, in turn, produce ova ; 



D. (1) These ova are developed into Medusse, thus 

 completing the cycle opened at A. 



T>. (2) These ova are developed into Polypes, thus 

 completing the cycle opened at C. 



The budding process, which both Medusa and 

 Polype manifest, may be eliminated from the scheme 

 of " Alternation." We shall hereafter see that it is 

 essentially the same as the other processes of gener- 

 ation. 



Such, in brief, is the history, such are the facts, of 

 Parthenogenesis. Let us now glance at the theories 

 which attempt to explain them. Steenstrup — whose 

 merits are very considerable, and who first propounded 

 a general theory, named by him the " Alternation of 

 generations" — encumbered the question, instead of 

 clearing it, when he called the Polype the " wet-nurse " 

 of the Medusa, denpng its claim to be considered as 

 a " parent." To say that the Polype is not properly a 

 '•' parent," but has only the germs of the Medusa con- 

 fided to it, is, as Professor Owen justly remarked, to 

 make a metaphor supply the place of an explanation. 

 In reply to this objection Steenstrup boldly declares 

 his theory is la comhinaison intime desfaits. Pro- 

 fessor Owen convincingly shows that the theory is 

 purely verbal ; and I would hold that it is in direct an- 

 tagonism with the fact that the Polype sometimes pro- 

 duces eggs without the mediation of a Medusa ; and 

 if a Polype, issuing from an egg, and also producing 

 an egg from which another Polype will issue, be not 



