STEENSTRUP'S THEORY. 299 



the facts I have brought foi-ward respecting the Polypes are 

 thus seen to stand in no absolute isolation. 



Eesuming in one schema the results of the investigations 

 into Polypes, with those of my predecessors, we find, — 



A. The Medusa parent produces ova ; 



B. These ova are developed through an infusorial stage 

 into Polypes ; 



C. These Polypes, in turn, produce ova ; 



D. (1 ) These ova are developed into Medusas, thus com- 

 pleting the cycle opened at A. 



D. (2) These ova are developed iiito Polypes, thus com- 

 pleting the cycle opened at C. 



The budding process, which both Medusa and Polype mani- 

 fest, may be eliminated from the scheme of "Alternation." 

 We shall hereafter see that it is essentially the same as the 

 other processes of generation. 



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

 thenogenesis. 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, denying its claim to be con- 

 sidered as a " parent." To say that the Polype is not pro- 

 perly a "parent," but has only the germs of the Medusa 

 confided 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 combinaison intime des faits. Professor Owen con- 



