CRITICISM OF OWEN'S THEORY. 307 



ill a room the temperature of wliicli was constant, and saw 

 these larvn3 produce broods for four years without interrup- 

 tion ! Whereas, had the temperature varied, these larvae 

 woukl have manifested changes similar to those obsei-ved in 

 ordinary circumstances, when the lowering of the tempera- 

 ture in autumn stops the production of larvae, and induces 

 that of perfect insects. We may also refer to the observation 

 of Sir J. G. Dalyell, who kept a strohila for several years 

 continually budding. 



A fourth and last objection is, that the Polypidom, which 

 produces both Polypes and Medusae by gemmation, also pro- 

 duces eggs which become Polypes, as every one knows, and 

 eggs wliich become Medusae, as I have discovered ; yet, after 

 one of these egg capsules has been developed on the Polypi- 

 dom, the budding process continues as before. This would 

 imply that the original prolific force, when nearly exhausted, 

 produced eggs, and then, suddenly recovering its vigour, con- 

 tinued the production of buds. Now, an oscillating force of 

 this kind cannot be accepted. 



Although I think Owen's theoiy must be abandoned, it 

 seems to me incomparably the best which has been offered — 

 indeed, the only one which goes deeper than a phrase, and 

 rests on definite conditions. The very definiteness of these 

 conditions enables them to be closely tested and confronted 

 with fact. The pregnant ideas contained in his work have 

 been of essential service in the formation of those conclusions 

 which force me to regard Parthenogenesis as not presenting 

 any jyecidiai' mysteiy. I shall endeavour to show that it is 

 no deviation fi'om the ordinary processes of Reproduction, 



