248 COMPENDIUM OF GENERAL BOTANY. 



one thing in common. It is, that the present condition of the 

 organic kingdom was brought about b}' individual variations and 

 the survival of the fittest in the struggle for existence. 



(Competition or the struggle for existence in both the plant and 

 animal world is, according to our opinion, a fact, caused on the one 

 hand by the excessive productiveness of the created organisms and 

 on the other bj the constancy of the available area of the earth's 

 surface. This competition is further necessary in establishing a 

 beneficent equilibrium in nature.) 



In Darwin's theory of selection, erratic variation is the j9r^j96'Z- 

 ling factor, sehction is \\\q prngrei^^siiKj and ordering factor. Accord- 

 ing to Njigeli's theory, variation is both the propelling ?k\\(\ j)rogres- 

 sing factor. Selection — that is, the survival of the individuals best 

 adapted to the environment — is, according to Darwin, the chief 

 means of evolution or perfection ; according to Niigeli, competition is 

 wholly without influence toward advancing from a lower to a higher ; 

 it onlv removes that which is less capable of existing. According: 

 to this autlior, an alga would have ])een converted into an oak, an 

 amceba into a mammal, even without competition ; only there would 

 be in addition all the descendants vvliich have gone out of existence 

 as the result of com})etition. 



So much concerning the difference between these two theories. 

 We shall now give some of IS^iigeli's objections to Darwin's theory 

 of selection which we believe to be important. 



1. The undetermined effects of undetermined causes presents so 

 much which is accidental that t\y\?, erratic variation in selection can- 

 not be harmonized with scientific thought. 



2. Tlie crosses of varieties due to natural causes are different 

 from those of artificially produced varieties. Natural varieties fuse 

 or cross with difficulty, and are not changed by such a process. 



3. Useful variations appear only when the variations have ad- 

 vanced to a considerable degree and have affected a large number of 

 individuals, thus enabling them to crowd out competitors. But 

 since variations must continue for a long time on a small scale, and 

 can exist only in a few individuals during that time, it is evident 

 that a struggle for existence and natural selection cannot come into 

 play. The following is an example given by Nageli : the progeni- 

 tors of our ruminants were hornless; due to variation, a few of 

 them developed microscopic horns. Since within the first fifty or 

 more senerations these horns must have been functionless on 



