238 COOK 



But no cause is lost without contributing something to the 

 progress of science. 



The attempted resuscitation of the saltatory theory and the 

 Mendelian "laws" has resulted in a new and more thorough 

 survey of this part of the field of variation, the same ground 

 which had been canvassed by Darwin's contemporaries and 

 critics, Mivart and Galton. But the general implications of the 

 facts do not appear to be very seriousl}^ altered. Darwin con- 

 sidered the possibilities of saltatory evolution, but dismissed the 

 idea as of incidental significance only. Galton estimated the value 

 of discontinuous variation much higher than Darwin, but was not 

 misled into the hazardous conjecture that saltator}?^ variations 

 cause evolution by originating new species. 



Darwin did not imagine that he had solved the problem of 

 evolution in the sense of having definitely ascertained the nature 

 of the motion or the causes of the variations by which it goes 

 forward. He was solicitous rather to make the doctrine appear 

 sufficiently reasonable to secure the serious attention of the 

 scientific world. He did not have complete confidence in the 

 foundations of his own colossal idea, and labored hard on 

 natural selection and other unnecessary scaffolding to support 

 it. Later criticism is removing these superfluous theoretical 

 timbers, but the primar}^ conception of evolution as a process 

 of gradual change in the characters of species, not only re- 

 mains intact, but stands forth with increased assurance of truth 

 and permanence. 



CONCLUSIONS. 



A typical experiment in Mendelism, instead of involving two 

 successive crosses or conjugations of gametes, includes only 

 one such cross. The so-called first generation is built up by 

 the vegetative subdivisions of the gamete parents, before con- 

 jugation is completed. The so-called second generation rep- 

 resents the first organisms produced after the completion of the 

 conjugation of the gamete parents. 



The difference of proportion between the two generations in 

 the expression of divergent parental characters is to be explained 

 by the peculiar methods of reproduction followed by the higher 

 plants and animals, and by the fact of dominance or expression- 



