28 CALIFORNIA ACADEMY OF SCIENCES. 



is the selection to be made? " No other mammals," he 

 says, have ever been stated to possess two little symmet- 

 rical excrescences on their frontal bones as an occasional 

 variation; what then caused such excrescences to appear 

 in the ancestors of horned ruminants? Butting with 

 the forehead would produce them, and no other cause 

 can be suggested which would." 



An inconsistency which has been pointed out by 

 Romanes, Osborn and Le Conte, is the fact that the Neo- 

 Darwinians admit the Lamarckian factors among proto- 

 zoa. Romanes has pointed this out with especial clear- 

 ness in his article entitled " Weismann's Theory of 

 Heredity."'^'' He calls attention to the fact that inas- 

 much as natural selection is unavailing without varia- 

 tion, and that variation, according to Weismann's view 

 is due to the sexual admixture of different traits, there 

 can be no individual variation among unicellular and 

 parthenogenetic organisms, and hence natural selec- 

 tion cannot be a factor in producing new forms. Weis- 

 manii, indeed, sees this to be the case and admits that 

 uiodifications in such animals must be due solely to the 

 direct action of the environment. Two objections have 

 here been interposed. Prof. Osborn asks why, if the 

 direct action of tlie environment was once a factor of 

 evolution, as Weismann admits,- it should ever have 

 ceased to be such if its period of usefulness did not ter- 

 minate.! Now it is apparent that the period of useful- 

 ness of the Lamarckian factors does not terminate with 

 the protozoa, and consequently natural selection itself 

 would have tended to preserve them. Prof. Romanes' 

 suggestion was not stated in the form of an objection, 

 although such is clearly implied. It is in brief as fol- 



" Contemporary Keview, May, 1890, pp. 686-699. 



tAinericau Naturalist, xxiii, ji. 



