Nos. 618-619] THE ROLE OE REPRODUCTION 



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gametic mutation. If one compares asexual and sexual 

 reproduction from the standpoint of frequency of varia- 

 tion only, then sexual reproduction may seem to hold the 

 advantage over asexual reproduction in the usual sense; 

 but parthenogenesis, which is certainly a form of asexual 

 reproduction, is in theory better adapted than sexual re- 

 production for giving large numbers of variations. 



If, therefore, one is constrained to agree that the bulk 

 of the evidence points to a practically identical coefficient 

 of heredity for both forms of reproduction, and that varia- 

 tion in the sense of actual changes in germinal constitu- 

 tion may occur with greater frequency in asexual repro- 

 duction, if there is any difference at all between the two 

 form-, he is driven either to the conclusion of Maupas 

 that continued asexual reproduction is impossible through 

 some protoplasmic limitation or to the conclusion of Weis- 

 mann that a mixture of germplasms offers sufficient ad- 

 vantages to account for everything. This is the dilemma 3 

 unless one wishes to maintain that efficient mechanisms 

 for nutrition, adaptation, protection and distribution 

 could not be evolved or maintained under asexual re- 

 production. 



The contention of Maupas can not be dealt with experi- 

 mentally any more successfully than the question as to 

 the inheritance of acquired characters since experimental 

 time and evolutionary time are not of the same order of 

 magnitude. The long-continued experiments of Wood- 

 ruff in which vigorous strains of Paramecium have been 

 kept dividing a sexually for several thousand generations, 

 however, as well as the botanical evidence that numerous 

 species having no sexual means of multiplication have 

 continued to exist during long periods of time, weight the 

 balance against him. One need not hesitate to concede 

 that all of these organisms are rather low unspecialized 

 types ; the modern development of genetics has built up 

 such a solid structure in favor of Weismann's view that 

 there is little need of argument along the older line. • 



