122 CALIFORNIA ACADEMY OF SCEENCES. 



physiological selection demands, the chance of all the 

 necessary contingencies arising contemporaneously 

 would be so slight^ as to make the theory unworkable. 

 Mr. Seebohm says: " To make it work we must pre- 

 suppose: — 1st, the special variation of the reproductive 

 organs must occur in two inviduals, otherwise the pos- 

 sible ancestor of the new species would have no 

 descendants; 2nd, it must occur at the same time in both; 

 3d, it must occur at the same place; 4th, the two indi- 

 viduals must be of opposite sexes; 5th, they must each of 

 them possess some other variation, or their progeny 

 would not differ from that of the rest of the species; and 

 6th, the variation must be the same in both, or appear 

 simultaneously in the majority of their children, other- 

 wise it would be swamped by interbreeding within the 

 physiologically isolated family ^" Obviously Mr. See- 

 bohm does not think it possible for all these contingen- 

 cies to be realized, and that from their failure to 

 co-operate the theory of physiological selection must 

 break down. 



Along the same lines as this Mr. Wallace also objects 

 to the segregation of the fit. In reply, Mr. Romanes 

 asserts that while it is true that the chances against 

 these physiologically isolated individuals mating may 

 indeed be thousands to one, so is it also true that the 

 number of fertile unions among animals com- 

 pared to the origination of every new species is in the 

 proportion of thousands to one, and he says: " I con- 

 fess it appears to me a somewhat feeble criticism to 

 represent that the conditions which my theory requires 

 for the origin of a new species are probably about 

 as rare in their occurrence as is the result which 

 they are supposed to produce." He furthermore states 

 that the variations in fertility of the sexual organs are 

 not due to chance, as his critics have assumed. They 



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